Merge pull request #36 from tPl0ch/feature/purge-mode

Add constant to be able to change purge mode for fixtures.
Make it possible to disable fixture autoloading

- Adding vendor and composer.lock to .gitignore
- Making it possible to manually load fixtures and rely on automagic reloading between tests.
- Minor refactoring
Merge branch 'feature-disable-autoloading' into master-fixed