Allow use of BackboneMixin without arguments; fix controlled components and changing models

[EamonNerbonne]

This PR builds on @markijbema's #15.

It fixes two subtle bugs:

1. When the model was changed due to a prop change, the event handlers were not rebound properly. This PR rebinds them correctly.
2. When the model was updated, due to the debounce, controlled components would lose cursor positoin. This PR avoids the debounce for models, and only debounces collections. Note that this still isn't an ideal situation - really we'd want to fix this on the React side of things, such that forceUpdates aren't immediate, because it's just wasteful to re-render all the time (and this isn't the only way to cause re-renders).

It also supports using BackboneMixin without arguments.

[markijbema]

👍

[clayallsopp]

This is great - @markijbema did you ever revisit this? #15 (comment)

[markijbema]

No sorry, didn't get around to doing that yet.

[EamonNerbonne]

However, I just did :-)

Behavior is slightly tricky (backwards compat often is, alas): change options are now those customized if available, otherwise the component (spec's) changeOptions, otherwise a default based on whether the model is a collection or just a model.

[markijbema]

👍 this was exactly what I wanted to do, thanks @EamonNerbonne !

[clayallsopp]

It is done! Thank you both very much for all the work, apologies for the extraordinarily long delay 👏