Issue #9: Add command line support for 'quiet mode', so that git-risk can be run from the command line and only output the results in terms of potential regression(s).
Issue #9: Refactor GitRisk object to include outputResults() so that everything is contained within a single object.
Issue #9: Refactor GitRisk object to encapsulate "quiet mode" inside of it as a setting, rather than passing it to the output function, for clarity.