removing delete operator where possible
Fix for #70, options.columns is not propagated to relations

Fix for #70, omitting options.columns when eager
loading relations.

Internal refactoring of the Collection object to match
the Model, adding the _handleResponse and _handleEager
methods. Test cleanup to match the mocha-as-promised
syntax universally.
documentation updates for 0.5.3
release 0.5.3