Run tests and code checks on Travis CI

![Travis CI](http://about.travis-ci.org/) is a continuous integration project for open-source projects. It shows whether the build passes or fails due to some error on each commit. Also it shows nice status for pull-requests - either they break tests or not.

This branch does the following:
 * Installs requirements
 * Runs self-tests (ported to ```python-nose```) to make sure that changes didn't break anything
 * Stores coverage report on ![coveralls](http://coveralls.io). See ![sample report](https://coveralls.io/builds/238117)

All of those steps are repeated for supported python versions (currently only 2.7) so we can see if the change broke 2.6 or incompatible with 3.3 etc.) when other versions will be supported

Currently travis will show many errors, but it would be easy to identify failing parts using pyflakes + pep8.

This script can be extended:
 * Run ```pyflakes``` to eliminate possible errors in the code (e.g. missing imports, mistyped variables etc.)
 * Run ```pep8``` check to ensure that code style is not broken (thus closing issue #37)
 * Build debian/ubuntu/whatever package and upload it to repository
 * Run other scripts/tests
 * Verify HTML/JS