Added error codes description.
Unit tests for DAO classes
Bug fixed: user registering to a nonexistent chat room.
Merge pull request #17 from slovit/Unit-tests-for-Dao-and-Service-classes

Unit tests for dao and service classes
Merge pull request #18 from slovit/Get-Endpoint-Implementation

Added error codes description.
MySQL configuration
Merge branch 'develop' into mysql-configuration
Implemented login endpoint