Fix: unload record with relationships

- calling `clearRelationships` before changing record state,
  otherwise it fails, because properties try to update removed
  relationships

- Transaction commit failed when an unloaded record was in the
  `transaction.bucketForType.updated` array. Using recordIsMoving fixed
  this issue
Only setting content-type to JSON if there actually is content.
Merge branch 'master' of github.com:enyo/data
Added a test for the content-type.
fix test description
fixed issue #582
added adapter integration test for dirtyRecordsForAttributeChange
Failing test: 'When a record is loaded a second time, isLoaded should stay true'
Add docs directory with package.json and yuidoc.json

`EMBER_PATH=../ember-data rake preview` in ember-website does not quite
work yet. I don't have time at the moment to get it working completely,
but let's have the docs directory as a starting point.
Add live query test for RecordArray
Potential fix for #731
Add Ember.Date.parse to fix cross browser bugs parsing ISO-8601 dates
removed vendored handlebars, gemified ember-data. no longer test with
jQuery 1.7 since hasn't been compatible with Ember for a while
DS.FixtureAdapter writes changes to FIXTURES
Integration test for DS.FixtureAdapter
Rename storeFixture
Fix typo in the comment on Primary key overriding options
Merge pull request #761 from machty/gemified

removed vendored handlebars, gemified ember-data. no longer test with
Merge pull request #765 from dybskiy/master

Fix typo in the comment on Primary key overriding options
FixtureSerializer correctly serializes associations