Add composer test script

[MaxGfeller]

Composer supports defining custom scripts. Major PHP projects started adapting this and are now all defining their own test scripts. Here are some examples:

• https://github.com/composer/composer/blob/master/composer.json#L63-L65
• https://github.com/Seldaek/monolog/blob/master/composer.json#L60-L63

The advantage of this is pretty obvious; you don't have to have a global phpunit/whatever setup and can just run composer test for each library that you want to start working with.

[mnapoli]

Why not :) But in that case it would be better to run vendor/bin/phpunit right (instead of using the potentially-missing global install)? Or does it look for phpunit inside vendor/bin already?

[jdreesen]

Seems like it prefers installs in vendor/bin by adding it to the PATH: composer/composer@cec1627#diff-b2f91f0223a25c1d2dc7fff236c4dfa4R57

[mnapoli]

👍 awesome

[MaxGfeller]

Yep, the cool thing is that 'composer run-script' adds 'vendor/bin' to the $PATH.

Thanks for merging!