Bump Mix dependency

Normally, words that start with vowels (like "unified") are preceded by "an" instead of "a."  However, "unified" is an exception to the rule.

Source: https://www.a-or-an.com/a_an/unified

[5.4] Change PUSHER enviroment variable names

[5.4] Remove compile.php

It's not used anymore.

Revert "[5.4] Change PUSHER enviroment variable names"

[5.4] Change PUSHER enviroment variable names

pusher.com's copy and paste .env snippet uses enviroment variables that
all start with "PUSHER_APP". This commit brings the config files in line
with pusher.com

These are very similar to routes in that they are channel endpoints
that your application supports and they also fully support route model
binding in Laravel 5.4. Upgraded applications do not need to make this
change if they do not want to.

[5.4] Added tinker to the default app

[5.4] Remove the "mail" driver as recommended, and add "array"

[5.3] Sort Composer packages by default