produce maven artifacts in library/build/mvn-repo/

I modified library/build.gradle to produce maven artifacts in library/build/mvn-repo/, hoping this helps with #2. If you're opposed to the idea of publishing on Maven Central please consider publishing to github by creating a separate repository or special-case branch for the maven artifact. For an example of hosting maven artifacts on github please see: https://github.com/WhisperSystems/maven

This pull also makes it easy for users to package and publish their own artifact of the project but personally I would prefer to use something packaged by the author :) thanks for the great project