Room service unit tests (part).
Amended service classes to conform to the Singleton pattern. Added more
test cases.
Implemented login endpoint
Created unit tests for Pull Request History and User Service.
Move test classes to test scope
Merged in develop branch
Merge pull request #19 from slovit/Unit-tests-for-Dao-and-Service-classes

Unit tests and fixing bugs.
Merge branch 'develop' into feature/login-endpoint