Currently there's no test coverage on CLI. This adds tests for a new class Parser which will replace the command line options currently in bin/annotate.

The technical direction I'm planning to go is to remove ENV variables completely and to have things passed into as arguments. Will be adding deprecation warnings in 3.0 and then deprecate ENV variables completely in 3.1. Deprecation warnings will be non-blocking in 3.0 when an ENV variable is set and an argument isn't passed in, and will becoming blocking in 3.1.