Fix #2228 - Add `findWhere` for parity with underscore
Bugfix to tests for Backbone.Collection underscore methods.
`_.include` was not being called correctly.
Documentation for Collection#slice
Merge branch 'document_collection_slice' of git://github.com/lukeasrodgers/backbone

Documentation for Collection#slice
Add link to MDN for Array#slice
Use `update` as default `fetch` method