Support rule tagging for location rules

[jasonrhaas]

Currently the _find_rule_matches method does not work for location rules. This is because the Twitter API requires 2 pairs of lat,lon coordinates which define the corners of a bounding box, but the twitter dataset defines an array of 4 lat, lon pairs.

There might be something tricky we can do to make this work but for rule tagging for location rules is not supported.