Merge pull request #134 from greboid/unittests

Unit test beep command.
Tidy up gradle source sets.

This replaces the default source directories (src/main/java, etc)
with our own, instead of just appending ours to the list.
Merge pull request #135 from csmith/master

Tidy up gradle source sets.
Gradle version bump.
Merge pull request #136 from csmith/master

Gradle version bump.