[OH-Dev] Class-based missions have landed (partially)

[Asheesh Laroia]

Hey all,

One thing we've been talking about for a while is refactoring the training 
missions so that they uses classes. Those have landed! You can read "How 
to write a training mission" documentation here; 
http://openhatch.readthedocs.org/en/latest/tutorials/writing_missions.html

I say they've landed "partially" because so far, the current class-based 
missions rewrite has only been applied to the "Windows setup mission". We 
need to take some time to apply it to other training missions. (Jacquie, 
this was something you were interested in, but the previous code was much 
messier. Now things should be way cleaner of you want to do that.)

Thanks to Nathan Yergler for collaborating on design and patches over a 
few OH sprints, and for submitting it for review. I had attempted to merge 
it in at the last sprint, but discovered at the last minute that it 
conflicted with the Subversion training mission. Today, I addressed that 
by adding a small commit on top of his work which fixed those test 
failures. Additionally, I tested the missions interactively on my 
development environment before pushing and deploying.

I'm really excited about this branch, and moreover, the fact that it's 
landed in master. Training missions will be simpler, and with more shared 
code (and less duplicated code) (and therefore, I believe, fewer bugs).

-- Asheesh.