Add docstrings for setnames! etc.

[pdeffebach]

There are currently no docstrings for a lot of publicly exposed functions in this package. It would be great to add them.

[davidavdav]

Yes you are absolutely right, I should take the effort to do this. Documentation of this package is pretty poor as it is, anyway.

[cvigilv]

Need help with this? I can invest a couple of hours converting the README.md into docstrings? I use this package way to much not to help a little with some documentation and examples.

[davidavdav]

Yes, I made a start with some documentation, I don't know how that would work.

If you send a PR that would be appreciated!