Updates `ember-dev` to (b0b12c4).

Updates `ember-dev` to (b0b12c4) which includes the following changes:

* Will not attempt to `unshallow` a full git repo
* Makes default test suite (packages only) run with features enabled and
  disabled.
* Fixes bug where the wrong Project name is used in the auto-generated
  CHANGELOG.
* Allows overriding the build type. (Simply set `ENV['BUILD_TYPE']='canary'`)
* Add `ember:generate_static_test_site` task to create a static HTML
  file for running the test suite.
* Add custom test results gathering for use in cross-browser testing.
* Make sure that the test file being used in the `Assetfile` is prefixed
  with the proper dasherized project name (prior to this Ember Data
  tests were still named `ember-tests.js` and now they will be
  `ember-data-tests.js`).
* Fixes issue where local `rake test` runs would attempt to perform git
  operations (`checkout` and `cherry-pick`). Now git operations will
  only be attempted if `ENV['CI']=true`.

For further reference:

https://github.com/emberjs/ember-dev/compare/0c0743979a...b0b12c4758e26
Merge pull request #3591 from rjackson/update_ember-dev

Updates `ember-dev` to (b0b12c4).