Add more README files into various subfolders

[aaronfranke]

Right now, it seems that the only README.md file is in the root directory of this repo. It would be helpful if there were more README files inside of other directories to help explain them. This would serve as documentation that is readable directly from GitHub or in a text editor.

For example, the "examples" directory could have a README file explaining what these are, how to run them, and perhaps larger ones could have their own README with further explanation.

Similarly, the "Extras" folder could use README files that explain what each of these extra components do, and how to use them.