Changing behavior isExpired to check `expireAt`.

We used to use a cacheable property to mark the resource state of an object as expired. Now we just check the time.

Conflicts:
	spec/javascripts/resourceSpec.js
Disabling a couple of autofetch specs.

Will be removing autofetch soon.
We can't rely on `resourceState` to check if an object is expired.
added refresh
removed unused updateIsExpired method
Fixed isFetchable

- Made it use the right property to check for expiry
- Made it volatile, as it depends on a volatile property now
- Added a test for it.
Refactored resourceSpec
Merge pull request #12 from zendesk/shajith/port_fixes

Porting expiry changes