Remove nginx version number as a security best practice. Hat tip to Remy van Elst.
Merge pull request #78 from gitlabhq/nginx-version-leak

Remove nginx version number as a security best practice. Hat tip to Remy...
Removed unicorn; added puma
Added missing option -d for puma options
Add RVM support for GitLab init-script on CentOS.

The origin init-script does not support the Ruby installed by RVM, now add the RVM bin folder to PATH to support it.