initial working version, tested on ubuntu.
remove mongo server from requirements
Merge pull request #236 from edx/jbau-edxapp-no-install-mongoserver

remove mongo server from requirements
Handle cases where we need to refresh ruby-build due to new ruby version
Merge pull request #239 from edx/e0d/datadog

initial working version, tested on ubuntu.
Merge pull request #237 from edx/jbau/ruby/always-update-ruby-build

Handle cases where we need to refresh ruby-build due to new ruby version