Dev Challenge

This code is ready to interact with my docker_server backend, which can be located at github.com/teddythetwig/docker_builder.

- Added a challenge creation interface to ActiveAdmin
- Created the models, views, and controllors for Challenge and ChallengeAttempt
- Implemented OmniAuth sign_up

With more time I would like to:

- Create gem that can interface with docker_builder
- Internationalize more of the application
- More frontend work

Issues:

Currently, there are a few issues that I have yet to work out. 
- Problem with strings being escaped on the builder_server
- Determining from output if solution passed


Thanks for putting this challenge together for me, I really enjoyed it.