Add quiet mode and support for ignore patterns

[timmkrause]

#39

[timmkrause]

Regarding ignore patterns:

I have wrapped them into an object to allow future extensions. One example could be to scope a pattern to certain files via file globs.

Another reason could be to additionally allow the following:

{
    "ignorePatterns": [
        {
            pattern: "^http://example.net",
            reason: "Some justification why this sould be skipped."
        }
    ]
}

[timmkrause]

Also addresses #10 and #18.

[tcort]

Thanks for the patches. Published in v3.5.0.