Created example unit test, instructions on how to set it up

Committing now that I finally got it set up.
Steps to make it work (the project settings to handle this don't appear
to be committed):
1. Run -> Edit Configurations
2. Add an "Android Tests" config, name it whatever
3. Choose "All in package", set package to
edu.ucsb.cs.capstone.letmypeoplecode.smartrover.test
4. Add a filter in logcat to catch messages with "TestRunner" if you
want to see the test output