Pause Button

* pauses topology and details panel updates
* buffers requests
* un-pause plays back the buffered requests
* automatically un-pauses when topology is changed, or other node is
  clicked (then discards buffer)

Fixes #1025

client/app/scripts/utils/string-utils.js

@@ -42,3 +42,5 @@ export function formatMetric(value, opts) {
   const formatter = opts && formatters[opts.format] ? opts.format : 'number';
   return formatters[formatter](value);
 }
+
+export const formatDate = d3.time.format.iso;