0.10 14jan2015
* added unit_system option

0.9 08dec2014
* do not use with construction for managers

0.8 06dec2014
* update for weewx v3

0.7
* fixed VERSION tag
* use windSpeed rather than gust for 10 minute average wind bearing
* added binding option for loop or archive

0.6 31aug2014
* check for None values in wind speed

0.5 05jun2014
* ensure compatibility with mysql

0.4 03jun2014
* more partial packet fixes
* forgot the syslog import
* fixed name of config file stanza

0.3 03jun2014
* deal with None values from partial packets (e.g., from WMR100 stations)

0.2 29apr2014
* aggregate excluding previous period
* fix trend calculations
* parameterize the wind speed/dir avg intervals
* ensure NULL instead of None in output
* use barometer (slp) instead of pressure (gauge)
* calculate temperature trend

0.1 28apr2014
* initial release as packaged weewx extension
