Check whether support of both Python 2 and Python 3 versions in one module is feasible

[peterazmanov]

The main problem of repository by Demur Rumed (serpex/byteplay) (Python 3.4 support stated) is unreadable code, which makes maintenance of the code difficult to say the least. Also one can't track changes that were made to base stable version of byteplay.py by Noam Raphael (Python 2.7).

Plan:

1. Compare base version of byteplay.py (Python 2.7) with version by Demur Rumed (Python 3.4, first commit).
2. Apply changes with support of all Python versions.
3. Apply other commits with fixes from serpex/byteplay with support of all Python versions.
4. Rebase my fork on top of previous changes.