Install Librarian cookbooks if Cheffile exists

Functionality copied from test-kitchen as suggested by "tknerr".
Let cook command to run Librarian in integration tests
Update Manifest.txt
Merge pull request #155 from musicglue/master

Fix bundler invalid gemspec warning
Merge pull request #36 from tmatilai/librarian-support

Librarian-aware `knife solo cook`
Fix some contibutor links in the changelog