Adding lib/Wikia/tests & an ex. with WikiaLogger.

Added lib/Wikia/tests and an example with WikiaLogger. I also refactored
WikiaLogger slightly to remove the ident and reduce the instances to a
scalar. It simplifies things slightly and I don't think there will ever
be more than one instance at any given time.

I also made the loading of the Logger lazy. This should make testing
easier.