Refs #46 -- Add Py3 support.
Test of README build to HTML is now done with 'rst2html' command via tox.
Refs #46 - Fixed Python 2 and Python 3 compatibility in doctests related to string/unicode.
Minor changes in tox configuration file.
Refs #46 - Updated changelog.
Revert "Minor changes in tox configuration file."

This reverts commit cfb6964af3724865e3e53ff70a55565a6a59eb9d.
Fixed indentation in tox.ini file.
Introduced support of Python >= 3.3. Closes #46.