Bug fix and test coverage

* Fixed a bug where non-affected branches aren't incorrectly marked as vulnerable (If only release 5.5 is affected by the bug, then any version of 5.4 should not be marked as vulnerable).
* Added additional tests to improve coverage (at 66.6% for extra evil).
* Added option to specify rule file (to aid with testing and so we could potentially look at pulling a latest list from Github since vulnerabilities will be continually updated and using an online list before falling back to a local cached copy might be a good option to keep the user up to date)