[COOK-3025] Adding support for per-repo proxies

Signed-off-by: Sean OMeara <someara@opscode.com>
Version bump to v2.4.0
Version bump to v2.4.1
Add tests to cover exclude and failovermethod parameters
Helper to fill out the resource with all attributes in the input map
Refactor so that the helper is used for setting all attributes which are passed through
Parameterise the failovermethod for remi
Update to indicate that you can use any of the underlying yum_repository attributes