Code snippets are missing in documentation

[Emrys-Merlin]

First of all thanks for the very handy library!

I think there are some code snippets missing on the documentation homepage. For example navigate to https://python-fints.readthedocs.io/en/latest/reading.html. Then there are two colons in the first paragraph of text. And I think there should be some code behind them.

I attached a screenshot of the page. I visited the page using Mozilla Firefox 61.0.1 on an Ubuntu 16.04. If you need any other information, just let me know.

[raphaelm]

Fixed! :) ReadTheDocs was configured to generate the docs with Python 2, but our source is Python 3 only.