Python 2/3 compatibility

[aleskarovadi]

Hello!

I have made changes in the code of Rammbock library which add python 2.7 and python 3.4+ compatibility and drop support of python versions less than 2.7. Also I added configuration file for travis-ci - .travis.yml (where utests will be run).

I have tested these changes:

• utest: all tests pass with python 2.7 and python 3;
• atest: all critical tests pass with python 2.7, but three critical tests fail running with python 3 (atest_logs.zip). I haven't figured out what causes these errors. They are don't affect my project because I don't need the funtionality where the tests failed. Maybe someone will fix them, if I don't do it before.

Hope my pull request will help to add support of python 3 to this library.