Creating readme at the directory level

[schaffung]

The idea is to document for posterity. Now, python has sphinx and other ways of directly converting the code to a documented website ( though we have to do some configurations ). But, I believe that will be more of a "what's the API and class the module has", rather than the "why" and "how".

Let's keep this issue as long running. We can give PRs and actually add the Updates: # keyword during a commit. So do not close this issue.