Fix circular json.
fix requires and usedBy
Update the tests to support JSON serialization
Add missing `return`
Fix test case
Fix var hoisting bug
Test `@requires` with existing target function
Always type and name in JSON representation
Use standard promise API
Add required function to tests fixtures
Better test for `requires` annotation

Testing circular references and JSON representation.
Merge pull request #182 from SassDoc/fix-circula-json

Fix circula json See #181