In-repo docs vs wiki

[martin-sweeny]

In #16, @ryandeering said:

This is just a folder for any miscellaneous scripts we need or future documentation, since we won't be using the Github wiki but a readme instead.

I think some stuff is worth keeping in the wiki, and other stuff should be in the readme. Core installation instructions, for example, can be moved from the wiki into the readme; but details on extra steps (for example running in Docker or Python venv) can be held in the wiki