add versioned default delegate obj for implementing version-specific
built-in methods on the context.

add v4 links() delegate method

update tests
implement local dereferencing
- add context.scope()
- add URL simple wrapper around window.URL
- add Pointer JSON pointer implementation
- refactor Context slightly to use Pointer (needs more)
- add Cache (deref index)
- add deref_tests
- enable suite/ref and suite/refRemote although the remote
  ones currently fail
version bump (v0.0.7)