Issue #353: Date Ranges should honour timezone settings.

The problem here is that the date picker uses the date of the visitor’s
computer. This means that we have to take the site GMT offset, and add
the local computer’s GMT offset, and then compare the current date with
the offset date.
Fix JS Lint error
Fixed dropdown menu dates
Better timezone support for Carbon
Merge pull request #370 from lukecarbis/issue-353

Issue #353: Date Ranges should honour timezone settings.