Two proposals in this PR: Python 3.4 support and Exposing current tab instance in template

Both commits are independent (even though consecutive and you can merge both if your like them), both cover testing and documentation independently. Hope you accept them :)

In any case, thanks for your nice project.
Yes, you are right. Sorry for my mistake. Can you merge just the first
commit for Python 3 support? I will modify the PR if necessary on Monday.
If you want I can document this as suggested as well.