remove uneeded resolvers
Add MIT license identification to the Ruby gemspec
Fix code comment typos regarding handling backend errors
Merge pull request #1635 from balinterdi/invalid-error-comment-fixes

Fix code comment typos regarding handling backend errors
Spare a property lookup on the record
Merge pull request #1636 from balinterdi/spare-property-lookup

Spare a property lookup on the record
Merge pull request #1634 from nbibler/patch-1

Add MIT license identification to the Ruby gemspec
Allow async relationship changes and rollbacks.

* Proper relationship changes for async relationships.
* Proper rollback of relationships.
* Refactored DS.hasMany and DS.belongsTo.
* Added _relationship to DS.belongsTo (similar to _attributes in DS.attr).
* Allow didSetProperty to work with belongsTo relationships in model states.
* Fixed tests that were passing with old code but were not actually right.
* Don't maintainInvariant on manyToOne change if parent === child.parent
* Don't unnecessarily fetch an unloaded async hasMany during certain remove
  change operations

Relationship changes now propagate correctly and model.rollback() works on
both belongsTo and hasMany relationships. Quite a few tests still need to
be written.