Class 'GuzzleHttp\Post\PostFile' not found

I have some legacy Laravel project, which i'm trying to add "guzzlehttp/guzzle": "~5.0" to, so i'm running the command: composer require "guzzlehttp/guzzle:~5.0" to which the output is show as below. When i try to change the Mail Driver to mailgun this is the output:

FatalErrorException in MailgunTransport.php line 79:
Class 'GuzzleHttp\Post\PostFile' not found

Laravel Framework as locked in composer.lock: 5.0.33

This is all of composer.lock: https://pastebin.com/dBJjDBtJ

This is all of composer.json: https://pastebin.com/UQNhKkyA

This is the output of trying to run composer require "guzzlehttp/guzzle:~5.0"

  Problem 1
    - Conclusion: remove laravel/framework v5.0.33
    - Conclusion: don't install laravel/framework v5.0.33
    - ryannielson/shareable 1.0.0 requires illuminate/view 4.1.* -> satisfiable by illuminate/view[v4.1.0, v4.1.1, v4.1.10, v4.1.11, v4.1.12, v4.1.13, v4.1.14, v4.1.15, v4.1.16, v4.1.17, v4.1.18, v4.1.19, v4.1.2, v4.1.20, v4.1.21, v4.1.22, v4.1.23, v4.1.24, v4.1.25, v4.1.26, v4.1.27, v4.1.28, v4.1.29, v4.1.3, v4.1.30, v4.1.4, v4.1.5, v4.1.6, v4.1.7, v4.1.8, v4.1.9].
    - ryannielson/shareable 1.0.1 requires illuminate/view 4.1.* -> satisfiable by illuminate/view[v4.1.0, v4.1.1, v4.1.10, v4.1.11, v4.1.12, v4.1.13, v4.1.14, v4.1.15, v4.1.16, v4.1.17, v4.1.18, v4.1.19, v4.1.2, v4.1.20, v4.1.21, v4.1.22, v4.1.23, v4.1.24, v4.1.25, v4.1.26, v4.1.27, v4.1.28, v4.1.29, v4.1.3, v4.1.30, v4.1.4, v4.1.5, v4.1.6, v4.1.7, v4.1.8, v4.1.9].
    - ryannielson/shareable 1.0.2 requires illuminate/view 4.1.* -> satisfiable by illuminate/view[v4.1.0, v4.1.1, v4.1.10, v4.1.11, v4.1.12, v4.1.13, v4.1.14, v4.1.15, v4.1.16, v4.1.17, v4.1.18, v4.1.19, v4.1.2, v4.1.20, v4.1.21, v4.1.22, v4.1.23, v4.1.24, v4.1.25, v4.1.26, v4.1.27, v4.1.28, v4.1.29, v4.1.3, v4.1.30, v4.1.4, v4.1.5, v4.1.6, v4.1.7, v4.1.8, v4.1.9].
    - ryannielson/shareable 1.0.3 requires illuminate/view ~4.1 -> satisfiable by illuminate/view[v4.1.0, v4.1.1, v4.1.10, v4.1.11, v4.1.12, v4.1.13, v4.1.14, v4.1.15, v4.1.16, v4.1.17, v4.1.18, v4.1.19, v4.1.2, v4.1.20, v4.1.21, v4.1.22, v4.1.23, v4.1.24, v4.1.25, v4.1.26, v4.1.27, v4.1.28, v4.1.29, v4.1.3, v4.1.30, v4.1.4, v4.1.5, v4.1.6, v4.1.7, v4.1.8, v4.1.9, v4.2.1, v4.2.12, v4.2.16, v4.2.17, v4.2.2, v4.2.3, v4.2.4, v4.2.5, v4.2.6, v4.2.7, v4.2.8, v4.2.9].
    - ryannielson/shareable 1.0.4 requires illuminate/view ~4.1 -> satisfiable by illuminate/view[v4.1.0, v4.1.1, v4.1.10, v4.1.11, v4.1.12, v4.1.13, v4.1.14, v4.1.15, v4.1.16, v4.1.17, v4.1.18, v4.1.19, v4.1.2, v4.1.20, v4.1.21, v4.1.22, v4.1.23, v4.1.24, v4.1.25, v4.1.26, v4.1.27, v4.1.28, v4.1.29, v4.1.3, v4.1.30, v4.1.4, v4.1.5, v4.1.6, v4.1.7, v4.1.8, v4.1.9, v4.2.1, v4.2.12, v4.2.16, v4.2.17, v4.2.2, v4.2.3, v4.2.4, v4.2.5, v4.2.6, v4.2.7, v4.2.8, v4.2.9].
    - don't install illuminate/view v4.1.0|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.1|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.10|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.11|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.12|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.13|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.14|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.15|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.16|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.17|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.18|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.19|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.2|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.20|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.21|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.22|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.23|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.24|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.25|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.26|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.27|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.28|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.29|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.3|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.30|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.4|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.5|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.6|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.7|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.8|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.1.9|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.1|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.12|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.16|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.17|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.2|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.3|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.4|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.5|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.6|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.7|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.8|don't install laravel/framework v5.0.33
    - don't install illuminate/view v4.2.9|don't install laravel/framework v5.0.33
    - Installation request for laravel/framework (locked at v5.0.33, required as 5.0.*) -> satisfiable by laravel/framework[v5.0.33].
    - Installation request for ryannielson/shareable 1.0.* -> satisfiable by ryannielson/shareable[1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4].

I've already tried to run composer update, auto-load and deleted the cache.

Note: I'm really sorry if this is badly formatted or it's missing something, trying to learn as i go. Thanks!

via Chebli Mohamed