Added CONTRIBUTING.md file
Merge pull request #16 from Bladrak/contributing

Added CONTRIBUTING.md file
Updated for admin bootstrap3 compatibility
Minor update to installation.rst

- Updated reference to composer instead of deps file, in line 4.
- Fixed typo in line 60.
Merge pull request #18 from guillegr123/patch-1

Minor update to installation.rst
Merge pull request #17 from Bladrak/adminBootstrap

Updated for admin bootstrap3 compatibility
Merge remote-tracking branch 'refs/remotes/sonata-project/master'