Add moment-timezone, and update moment.js to meet it's minimum version requirement
Display times in a configurable timezone, defaulting to UTC.

This adds a new option, DISPLAY_TIMEZONE to config.py, and
makes all graphite, nvd3, and flot charts display results in
that timezone. I'm not happy with the change to flot.time.js,
but I wasn't able to find a better injection point.
Merge pull request #263 from markolson/configurable-timezone-displays

Configurable timezone displays