WIP on Definition and Query DSLs

 » Add Octokit gem for searching GitHub
 » Change GitHub service for using their API
 » Service shortcuts on Apronach main module
 » Tag shortcuts on Apronach main module
 » Other small changes...
Apronach main module shortcuts

 » Decide the "definitive" interface of the Apronach.query method
 » Create Service#alias method
 » Finish the interface of the service shortcuts
 » Finish the interface of the tag shortcuts
Apronach#query

 » Fix shortcuts
 » Add specs for its interface
Beginning Apronach#query interface
Refactor argument validation, creating a Util module
Finish Util module