Add README.md with Build Instructions

[johnwstanford]

Could we add a README with build instructions? It's not completely clear what the build system even is, although the .idea folder suggests that the IDE used for development is IntelliJ IDEA. Which version of the JDK are you testing it with? How would we build from the command line if we wanted to?

[johnwstanford]

I've gotten the build to work with Gradle, although it doesn't look like that's the build tool you're using. If you want to provide a more repeatable command line option, I could submit it in a pull request with some README.md instructions. Didn't want to complain without offering to help :)