Add some tests for lib.config

When developing some enhancements or features for SmartHome.py I'm still a little bit worried about if something will break after I change something.

To be sure the most functionality will still be working when changing the code base I want to introduce some tests - at least for the SmartHome.py core modules (e.g. reading/parsing the configuration files).

I started to introduce a new `tests` directory which contains (currently) a file called `test_config.py` which contains some tests for reading configuration files. Additionally it contains a `common.py` which is included in the test file to do some comon setup (e.g. setting up the Python module path).

The tests can now easily be run by using the `run.sh` script, which runs Python with the `unittest` module and run tests by using the discovery function of this module.

What do you think about writing tests?