pep8

translation-memory-tools claims on its README that the coding style used is ``pep8`` and that's great news!

Still a run of ``flake8`` on the src folder reveals quite a few mistakes... nearly 500 actually.

The most offending thing being using tabs instead of 4 spaces.

The attached commit is just a pep8ify of the shortest files, as a proof.

If there's really a desire of trying to enforce pep8 I can happily go over all the files and put them together beautifully.

Note that ``CamelCase`` synatx for naming is discouraged and non_camel_case naming is preferred. This would involve rewriting nearly all code to use this convention... how far do we want to enforce pep8? (that's an open question :)