Correct some lint on server side

Pylint complains about some little formatting that can indeed make the
code a little better. Other remarks were not corrected because they are
cosmetic and it's nicer like it is now.
Rewrite the client side controller in CoffeeScript

The client side controller has been rewritten using CoffeeScript. The
`app.js` is still versioned so the application is ready to be deployed
without the need of a CoffeeScript compiler.

The `app.js` can be regenerated with `coffee -c -o static/js
src/coffee/app.coffee`.
Add notice about python version in README.md

The code is written for Python 3 only but it is not made clear. A notice is added to the README.md so that every interested user is aware of this limitation. Python 2.7 may be supported later.
Support Python 2.7

Originally the application was only intended to be used with Python 3
and made use of statements and syntaxes that are not valid in Python 2.
It seems however, that the days of Python 2 are not over and some users
had interest in using the application with Python 2.

With the same codebase, the application now runs using Python 2.7, 3.3
and 3.4. This should close #1.

Signed-off-by: Cilyan Olowen <gaknar@gmail.com>
Merge commit '39605c5188db4f0eb84a04ffb8f6306e3fd4bdfb'
merge form.html
Merge commit '4ce697b02c6ce2388ed25c02eec2f39330ce8343'
Merge commit 'ce72ad7656304fcace3023117009005f1347ea48'