Update phpdocs (static return types)

Also made the Closure return consisten use \Closure and some small typos
Merge pull request #1728 from barryvdh/4.0

Add static return types to phpdocs
Allow ServiceProvider::commands to receive an array of commands
Add PHP 5.5 to travis config file for workbench packages

Signed-off-by: Dries Vints <dries.vints@gmail.com>
Merge pull request #1766 from driesvints/feature/add-php-5.5-to-workbench-travis-stub

Add PHP 5.5 to travis config file for workbench packages
Merge pull request #1746 from Anahkiasen/patch-1

Allow ServiceProvider::commands to receive an array of commands