Adding simple solution model
Adding simple solution uploader
Mount the SolutionUploader in the Solution model
Adding URL fetcher to download stuff from S3
Adding solution.source_code_content to get the content of the solution

* Change to the simpler HTTParty.
* Read the file when not in production.
* Download the file (and cache the content) when it's stored on S3.
Use a real solution in the _solution partial
Add active class to categories in the sidebar
Remove sample source code. No longer needed.
Test that we show errors when creating a judge.
Adding simple solutions controller
Remove full layout. Let controllers decide when the layout is full or not.

There's less duplication having just one layout and letting the controller
actions decide when to use or not the sidebar. This adds coupling between
layout & actions and adds a little bit of logic to the layout, but it's
better than having to change 2 files to make a global layout change.

Most actions should just use the non-full layout (by default we have a
sidebar), so this will not be a big problem.
Let users add solutions to problems.
Move away from Dummy problems to real problems on each section

Now that the models are (almost) complete, we can start using the real associations
instead of repeating dummy ones.
Redirect the user to where they wanted to be when login is needed.
Adding code climate badge
Merge pull request #6 from nhocki/solutions

Solutions models. This would be the first kind-of-usable version of Cómo Vamos.