Start building unit tests

This begins building unit tests starting with WPSC_Country (No reason, but had to start somewhere!). 

The test suite is incomplete, some methods flat-out aren't covered, some could do with more detailed tests. 

As things stand though there are a number of failures - including at least one test that causes a fatal error to be thrown (See test_get_region_code_by_region_id() and beyond in the test file). 

We should fix the fatals as a priority, then work on squashing the remaining test failures.