[WIP] Use gem version of rest-client

The patch that we forked for has been merged.

Unfortunately ssl v3 needs to be disabled, so we need to find an alternative here.

@gmcculloug @blomquisg do we have plans for ssl on RHEVM?
I don't think we need the comment on why we need to upgrade.  Perhaps in the commit message, but not needed in the Gemfile itself.

Where does it say that 1.7.0 is in alpha?  Looks fully released as far as I can tell from the repo.