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 
I don't get it. The `until` in the URL already correctly sets the end-time field within the graph controls. As far as I can see, the URL given by @grobie in https://github.com/prometheus/promdash/issues/192 works as intended (the graphs are showing the until-time specified in the URL, and the correct range). What am I missing?