v2.0.0

Here's the CHANGELOG I have so far (which will go into a [Release](https://github.com/afeld/backbone-nested/releases)).  Probably needs another pass through [the commits](https://github.com/afeld/backbone-nested/compare/v1.1.2...master) to find user-facing changes.

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* Backbone 1.x support (#96)
* add option to test from command line and run tests on Travis CI
* fix `remove()` not firing `'remove'` event when last element of array is removed (#19)
* fix `clear()` and set nested attributes on `changedAttributes()` (thanks @isakb)
* `'change'` events will no longer fire if new value matches the old