Improve documentation (automatically generate)

[yochem]

Problem

Documentation for the package is currently hard to use. The README lists the available methods, but they lack information (accepted types, example, difference with other methods, return value).

Solution

Generate docs from well-maintained docstrings after #144 is merged. The docs include the full interface of the package.

Considerations

• Generate HTML and host the docs online? This would probably be easiest on GitHub Pages: https://doceme.github.io/py-spidev.
• Another possibility is to find a way to convert the docs to markdown and include it in the README, with a similar results as to how it is now. (With https://niklasrosenstein.github.io/pydoc-markdown/?)

Let me know which approach you'll find most appealing. I'll start with it after #144 is merged.

[yochem]

Here's an example for a self-baked docs generator that writes to the README: https://gist.github.com/yochem/cf1af5c9efc659a0b1336d92aa05257b.

It's a <100 lines python script that mostly handles walking the SpiDev class and printing its methods signatures and the documentation. Of course the documentation still needs a lot of love, but this would allow us to at least have documentation that is correct.