Fix Python 2.6
First version with python3 support.

 * Moved requirements*.txt files to proper spec definitions in setup.py
 * Added a new fig.compat module to store some compatibility code
Added tox file
Fix exception alias syntax
Use print function
Add future import for print function
Add texttable compat module that is py3k compatible
More future imports for safety
e.explanation a 'str' object
Add unicode_literals to main module
Add Python 3 and PyPy to .travis.yml
Put requirements back in .txt files

Read-only FS in travis