Stub method for running unit tests.
Tests run if $TEST_OS is set in .config file.

If the $TEST_OS is set in the .config file then before building and
packaging, the unit tests are run. If the all the unit tests pass then the
script continues onto building and packaging. Otherwise it exists.

If the $TEST_OS is not set, then the script skips the unit tests.
Merge pull request #1 from 3squared/run-tests

Run tests