Updated source level to 1.7
Added an 'until' method which will pull kills until the pulled page has kills before the passed in date
updated tests so that they can test gzip capability... apparently zkill doesn't listen to Accept-Encoding: gzip though :/ so this isn't enabled.
Added User-Agent but left it commented out for now until I get around to implementing this in a safe manor so it can be set with a sensible default.