Increased test coverage for jUnit formatter.

Added a test case to bring test coverage of the jUnit formatter up to 100%.
Increased test coverage for `lib/rules.js`

Created a test case that increased the test coverage of `lib/rules.js` to 100%.
Increased test coverage for `lib/cli.js`.

Created a test case that increased the test coverage of the CLI.
Merge pull request #202 from iancmyers/testing-core-coverage

Increased test coverage for core lib and formatters