#130 - Use Nokogiri xml instead of slop in rspec.
#130 - More APIs moved to new Rails.

* Pipelines feed API.
* Stages feed API.
* Pipeline instance feed API.
* Had to move MaterialsHelper, ComparisonHelper and FeedsHelper for it.
* Had to move PipelinesController (pipelines_controller.rb) for it.
Merge pull request #218 from arvindsv/apis_to_new_rails

#130 - More APIs moved to new rails.