Makes marathon_client gem available to LWRP

Fixes #19 

Fixes issue where require statement in LWRP would fail due to
unavailable marathon_client gem. Gem is installed during parsing of
LWRP at compile time. Gems have been updated along with their
corresponding files, which includes style and tests.

Why not just use Chef::Resource::ChefGem here?

http://www.rubydoc.info/github/opscode/chef/Chef/Resource/ChefGem