Fix documentation for python wrapper and state vector

[skyreflectedinmirrors]

It's clear that having the Temperature be the first value in the state vector is causing confusion for new users (e.g. #14). We need to document both the expected structure of the state vector for (C/CUDA) and the python interface

[skyreflectedinmirrors]

WIP: added more documentation and examples.

@michael-a-hansen I'd also be interested in your feedback, to see if that explains things a bit more

[michael-a-hansen]

Looks good to me :). I don't think any of this is particularly complicated, so examples like this make it very straightforward.

[skyreflectedinmirrors]

Ok, I'm going to close it then! If there are any more examples you need please let us know!