Add ansible role to install packagecloud.

From the review comments by Andy:

Actually, I think Anil is correct that this really should be in an ansible role. If nothing else the ruby-dev install should be moved to our lf-dev-libs role, along with the rake gem install.

I would have no issue with the package_cloud install being put into the recommended tools role (I can't remember if that fires before the dev-libs, if it does, then ruby-dev and rake in that role as well).

In any case, since these are all being installed at the system level for gems, they really should be baked into the images.