Clean up Collection.isModified() tests a bit, and tweak Collection class doc.
Re-add data.persistence.request.Batch class. This may be used after all to batch Collection.sync() requests.

This reverts commit 3a12031c689987b4db526cca964ce339f40c3188.
Add getCreateRequests(), getUpdateRequests(), and getDestroyRequests() to data.persistence.request.Batch class.
Merge branch 'master' of github.com:gregjacobs/Data.js

Conflicts:
	src/Collection.js
Add getNewModels(), getUpdatedModels(), and getRemovedModels() methods to Collection. Also clean up some tests.
Change docs in Model/Collection classes to use the term "map" instead of "hash".
Change how Proxies interact with their given Request object. Instead of returning a new Deferred object from each of the CRUD methods of the Proxy, the Proxy now resolves or rejects the Request itself.

Also add `batch()` method to Proxy, which handles multiple create/update/destroy requests at once.
Change Proxy.batch() to also accept 'read' requests in addition to create/update/destroy.