Mms agent recipe enhancements

This includes a merge of upstream master, so use https://github.com/Kabam/chef-mongodb/compare/merge-upstream...mms-agent-recipe-enhancements to see the relevant changes. I will be putting this into a PR against upstream as well.

mms-agent recipe enhancements:
- fixed incorrect cookbook name reference
- agent install and log directories are now configurable as attributes
- switched to community runit instead of non-standard one
- detects if there's been an api key change which will trigger an
  agent restart
- detects if there's been an agent code update which will trigger an
  agent restart; note that this does NOT avoid a download
- misc README, doc, and metadata updates
- dev changes to Vagrantfile

Part of the work for https://www.pivotaltracker.com/story/show/56553362