Shapely: Automatic doc builds

[sgillies]

Automate our doc build and publication workflow using Travis's deploy system.

See also #336.

[pelson]

Incidentally, matplotlib does this already. See https://github.com/matplotlib/matplotlib/blob/master/.travis.yml#L126

I definitely think the process could be improved though...

[pelson]

Additionally, I just found out that ReadTheDocs can now do conda installations, making RTD a viable option for Shapely doc building (I did a proof of concept for Cartopy with some success).

[snorfalorpagus]

I've had a go at this and have something working, based on this tutorial: https://gist.github.com/domenic/ec8b0fc8ab45f39403dd

The changes are here: https://github.com/Toblerity/Shapely/compare/master...snorfalorpagus:autodoc

The process requires you to create a new SSH key pair and put an encrypted version of the private key into the repo / Travis.

It's set up to only build the documentation in one instance (the Python 3.5 with speedups). https://travis-ci.org/snorfalorpagus/Shapely/jobs/177188968

This has highlighted that quite a few of the scripts that create figures in the documentation aren't compatible with Python 3.x, e.g. buffer.py which gives:

Traceback (most recent call last):
  File "buffer.py", line 29, in <module>
    ax.set_xticks(range(*xrange) + [xrange[-1]])
TypeError: unsupported operand type(s) for +: 'range' and 'list'

[sgillies]

@snorfalorpagus before you spend more time on this, let me look into whether our manylinux1 wheels help make readthedocs a better option.

[pelson]

Also want to raise awareness of https://github.com/drdoctr/doctr if you do go down the docs on travis route.

[sgillies]

I'm moving this one to the next milestone. I'd like to unblock 1.6.0 and work on the doc infra after.