Laravel 5 laracasts flash messaging not showing error div

I've been trying to get a flash message letting the user know that their message from the contact form has successfully been sent, I found This Github Repo in which there's an "easy" way of flashing error messages in Laravel 5 (I'm using Laravel 5.2) so I went on an tried using it, but I can't seem to get it to work.

The classes are all being found, the problem here is that it won't flash after I redirect.

In my master.blade.php

@if (Session::has('flash_notification.message'))
<div class="alert alert-{{ Session::get('flash_notification.level') }}">
    <button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button>

    {{ Session::get('flash_notification.message') }}
</div>
@endif

In my routes.php

Route::post('sendemail', function () {

    $data = array(
        'name' => "Learning Laravel",
    );

    Mail::send('emails.welcome', $data, function ($message) {

        $message->from('email@provider', 'Learning Laravel!');

        $message->to('email@provider')->subject('Learning Laravel test email');

    });
        Flash::message('Thank you for contacting us, we will get back to you as soon as possible.');

        return Redirect::to('/');

});

What am I doing wrong / forgetting?

EDIT Complete routes.php

<?php

/*
|--------------------------------------------------------------------------
| Routes File
|--------------------------------------------------------------------------
|
| Here is where you will register all of the routes in an application.
| It's a breeze. Simply tell Laravel the URIs it should respond to
| and give it the controller to call when that URI is requested.
|
*/

Route::get('/', function () {
    return view('index');
});

Route::post('sendemail', function () {

    $data = array(
        'name' => "Learning Laravel",
    );

    Mail::send('emails.welcome', $data, function ($message) {

        $message->from('email@provider', 'Learning Laravel!');

        $message->to('email@provider')->subject('Learning Laravel test email');

    });
        Session::put('flash_notification.message', 'Thank you for contacting us, we will get back to you as soon as possible.');

        return Redirect::to('/');

});
/*
|--------------------------------------------------------------------------
| Application Routes
|--------------------------------------------------------------------------
|
| This route group applies the "web" middleware group to every route
| it contains. The "web" middleware group is defined in your HTTP
| kernel and includes session state, CSRF protection, and more.
|
*/

Route::group(['middleware' => ['web']], function () {
    //
});

via Chebli Mohamed