Bump to version 2.7.0

Add Gemfile
Add Berkshelf
Adding Gemfile/chefignore as part of move towards Vagrant/Berkshelf workflow

Moving startup command out of monit into its own script: puma_start.
Cleaning up puma_kill and make puma_start call puma_kill to ensure clean state even though puma 2.7.0 handles cruft better than before.