Refactor: Unit Test Services without DB Dependency

[joneubank]

The motivation for these changes was to be able to unit test the dictionary service without relying on Mongoose integration. To accomplish this, we add sinon to mock services and chai-as-promised to test the outcome of some async function results.

The major code changes made to support this change are:

1. The Dictionary model now exports methods that should be used to interact with the DB, including fetching a dictionary, listing dictionaries, and saving a new dictionary. These were moved out of the dictionaryService.
2. Rewrite tests on the dictionary service to mock db interaction calls.

Other Changes:

• New Endpoints: Mixed in with this work were two new endpoints to be able to fetch individual schemas, and fields from individual schemas through the API. This fulfills: Feature Request: Endpoints to query specific schema and fields within a dictionary #178
• Mocha configs were moved into a .mocharc.json file and are no longer set in the test scripts. This lets the VS Mocha plugin interact with the tests.
• Moving test fixture dictionaries around and removing references to external projects.

This PR depends on approval of: #181