Update to Python 3?

[drmstwizard]

Even using 2to3, this script relies on some variables that are unsupported by Python 3, and since Tumblr is on a bender of deleting innocuous blogs at the moment, it would be nice to be able to run the script again! Thank you.

[bbolli]

Duplicate of #96 which has a separate script that uses Python 3.