This adds some READMEs for both the main repository (for use on GitHub)

and for pydiffx (for use in the package) that describe DiffX as a whole

and pydiffx, respectively.
The pydiffx version is a shortened version of the main pydiffx

documentation, and links to the suitable spots in the main docs.
A LICENSE file was added to pydiffx and to the root of the repository.

This is the MIT license.

Viewed both READMEs through a viewer emulating GitHub. Tested each link.