Fix Issue #12, add unit tests for logging

Logging had a bug where .log was not defined, but was being used.  All current unit tests use the option silent = true, so tests would pass, while use of any method that referenced log.js would fail.

I have modified the _levels object to add log, and make use of info and warn for expected console.log output for different levels, as well as added a few very simple unit tests so future issues will fail testing.