Add walkthrough for examples.

Summary:
- Add walkthrough for each example file in `README.md`
- Remove unnecessary config file
- Add "ignore = dirty" for OpenWormData in `.gitmodules` which lets me more easily checkout branches with OpenWormData as a directory rather than a submodule

The last couple examples in the walkthrough have little instruction because they are more advanced, but someone with more knowledge should feel free to add to the descriptions in the README.

In all, this pull request should resolve the rest of #61.