Fixes #933, Fixes #908
Merge pull request #920 from braddunbar/$

use `$` as DOM abstraction library
Fixes #917 -- reverts validate() behavior to never run on silent sets.
Merge branch 'master' of github.com:documentcloud/backbone
#917, adding an Model#isValid() function.
Merge pull request #906 from tomasztunik/master

Fixes issue #904
options.silent respected in _prepareModel ... prepping for a 0.9.1
DRY-ing up _validate
merging in setDomLibrary
comments for setDomLibrary
Backbone.js 0.9.1
fixing changelog typo
editing the intro
removing obsolete error case.
Adding Wunderkit as an example app.
fixing typo in Wunderkit description
Refactor some tests.

* Use object for lastRequest to prevent errors.
* Ensure setDOMLibrary tests are cleaned up.
Merge pull request #940 from braddunbar/test-refactor

Refactor some tests.
Add tests for #906.
Adding the Khan Academy as an example app.