Merge pull request #17 from daanwissing/master

Fix README.md example of DateTime.format()
Document that < and > work out of the box.
Adjust changelog.
Performance optimization for DateTime.valueOf() and DateTime.unixUtcMillis() and < and > on DateTimes.
version 1.8.2
Bugfix in unixUtcMillis()
Version 1.9.0: added a Duration constructor for an amount of TimeUnits.
Upgrade to tz database 2014j.
Issue #18: Remove references to timezone-js.
Issue #18: Update example file to be usable out of the box.