Added colon (:) to allowed URL characters per RFC3986

Added colon (:) to allowed URL characters per RFC3986 (: defined as a general-delimiter, same as / ? # and @ ). Added test for colon.

Tests now break because "'file:///C:/Program Files'" is now matching, which was previously unmatched due to the colon. If local paths should not get linkified, something other than the colon should be used for filtering.