(ie. when neither zulu time or an offset is included, use local time). Add tests.
Rename `xLabelsFormat` -> `xLabelFormat` (grammatically better :)) Add note to example to recommend use of `xLabels` option when using `xLabelFormat`. Use $.extends rather than setting spec.fmt directly (avoids modifying the globals). Add a test.
xLabels
Clean up whitespace (hooray for Whitespace.tmbundle!).
