- Enabled tests in ``tox.ini`` and ``.travis.yml``
- Declare support for 3.6 in ``README.rst`` and ``docs/release_notes.rst``

As per [their blog post of the 27th April](https://blog.readthedocs.com/securing-subdomains/) ‘Securing subdomains’:

> Starting today, Read the Docs will start hosting projects from subdomains on the domain readthedocs.io, instead of on readthedocs.org. This change addresses some security concerns around site cookies while hosting user generated data on the same domain as our dashboard.

Test Plan: Manually visited all the links I’ve modified.

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
Reviewed-by: Amir Rachum <nurdok@gmail.com>

The requirement for an extra line at the end of a
multi-line docstring has been updated to only
require the closing quotes to be on a separate
line.

Ref: https://codereview.appspot.com/69870043