Add tox.ini for tox (http://tox.testrun.org/)
Add .tox to .gitignore
Fix relative import for Python 3
Change from except-comma syntax to except-as syntax for Python 3
compatibility
Make code Python 3 compatible
Merge branch 'tox' of git://github.com/msabramo/tldextract
Merge branch 'python3_no_2to3' of git://github.com/msabramo/tldextract