Develop

Coverage work:
 - grader3 specs and comments (in code to refer when doing refactoring in future) 
 - autograder - specs and comments
 - feature_grader - specs and comments
 - rvm files and .travis.yml added to .gitignore
 - travis: added downgrade of rubygems to resolve the bundle issue with ZenTest
 - commented requires for ruby-debug, for RubyMine debug to work
 - changed syntax in specs to remove deprecation warnings