Revert "Change vendor name in composer.json..."

This reverts commit 2ad8bac9e68a6a76d95c0fdf5e9a303ae936cd6b.

Earlier I thought that forking a project was part of Composer's workflow if you
wanted to use changes before they got approved by the main project maintainer.
Turns out there is a built in way of achieving this *without* creating a full-on
fork (http://getcomposer.org/doc/05-repositories.md#vcs), which is quite a
relief!