Updated the Bootstrap file to also include vendor autoloading

I've updated the Bootstrap file so it does check for /vendor/autoload.php and include it if existing, so that Modules installed via composer will be loaded, too.
Merge branch 'hotfix/#904'

Close #904
Merge branch 'patch-1' of https://github.com/manuakasam/zf2-documentation into hotfix/#902
Merge branch 'hotfix/#902' into develop

Close #902