[Closes #2] Added client & token entities.
[#5] Added rspec, rack, spark & guard to project.
[#5] Added mechanism for registering and viewing client repositories.
[#5] Added base error

 - consists of type, status & description
[Closes #5] Added client authenticator

 - Takes rack request

 - Authenticates params or authorisation header if present

 - retrieves api client from repositories given or registered