Added dev dependency for PHPUnit 4.
Updated travis to use dev dependency version of PHPUnit.
Added plugin context to the event object.

The plugin manager can now spawn an event that has context of itself.
This plugin context can be set externally on the event as well.
Corrected website link in composer.
Updated lock file for site link change.
Merge pull request #20 from zumba/plugin-event-generator

Plugin context event with generator.