Update tumblr2hugomarkdown.py

[CamMakoJ]

wouldn't run on my machine without brackets around print statements as well as an update of dependencies

[chillu]

As of now, this also needs an unreleased version of PyTumblr (newer than 0.1.0) to work. Fixed this with the following in requirements.txt

PyTumblr==git+https://github.com/tumblr/pytumblr.git@master