Provide a license and installation / usage details

Demo apps need to provide helpful details about how to install and use
them. Additionally, then need to outline the licensing restrictions for
their use.

Prep the new beta3 build.
Require a minimum Google Play version.

In order to prevent people from accidentally locking the app to the
latest Google Play (such as a pre-release), explicitly set a minimum.
Update demo code.

- Use the latest beta build for improved funcationality. Several bug
  fixes are included.
- Add helpful javadocs in the demo code. This helps people reviewing the
  demo understand what is going on within related methods.
- Add helpful inline comments to explain different parts, and the
  reasoning behind, of the code.
Merge pull request #2 from RadiusNetworks/update-with-beta

Update with beta