Add &until=now to frame url query strings missing until parameter.

Missing this parameter broke setting frame end time via query string, e.g. http://promdash/web-status#?range=30m&until=2014-09-24T17:53:52.223Z

addresses #192 
If the frame URL doesn't have an `until` value in it, then the `until` value in the query parameters does not get interpolated in (the same things happens when setting `range` but the original frame URL has no `range`). If no `until` exists in a graphite URL it defaults to `until=now`, but this makes that explicit so the query parameter value can be substituted.