Expose DatetimeTickFormatter.formats in Python API
Show how to use DatetimeTickFormatter in daylight.py example
Add DatetimeUnits enumeration for DatetimeTickFormatter.formats
Merge branch 'master' into datetime-formats
Sort DatetimeTickFormatter's formats by their "size"
Merge pull request #577 from mattpap/datetime-formats

Expose DatetimeTickFormatter.formats in Python API and add an example