Replace hardcoded curl with nanliu-staging's staging::file.

This replaces the hardcoded `curl` exec with a more flexible
downloader provided by nanliu-staging.  It can use wget or curl,
and will autodetect the right one to use.
Merge pull request #166 from apenney/nanliu-staging

Replace hardcoded curl with nanliu-staging's staging::file.
manage_repos:

   If +true+ it will try to setup the repositories provided by rabbitmq.com to
   install RabbitMQ. If you manage your own repositories for whatever reason you
   probably want to set this to +false+.
add spec tests
Update rabbitmq_spec.rb
Remove garethr/erlang dependency

Most of the distributions handle the erlang installation automatically.
The garethr/erlang dependency is not needed there and can be added
manually in case it's needed.
Merge pull request #135 from toabctl/remove-erlang-dependency

Remove garethr/erlang dependency
Merge pull request #140 from robocoder/manage-repos-patch

manage_repos