Clean up unneeded commented out code
Streamline and refactor RRD backend

 - Merge Visage::Collectd::RRDs into Visage::Collectd::JSON, to simplify
   code paths and consolidate backend access
 - Rename Visage::Collectd::JSON to Visage::Data, as it more accurately
   reflects what the class is meant to be doing.
 - Move duck punches into visage-app/patches, so they're all listed in
   one place.
 - Re-indent code.
Update tests to work with capybara
Make Visage::JSON query building cleaner:

 - Split method arguments out into separate hashes for readability.
 - Make whitespace consistent.
Refactor RRD support out into a pluggable backend
Add mock backend
Require the other files with the correct path
Remove last (hopefully) traces of webrat