Release v3.4.0b6

Add support the new Weather Underground API. The new API provides for a 5 day forecast (6 days if you count the current day).

Only the API key needs to be specified in weewx.conf:
[[WU]]
api_key = XXXXXXXXXXXXXXXXXXXXXXXXXXX

In the above case, the station’s lat/long will be used to retrieve the forecast.

If needed, the following may be specified. The extension will look for these in this order and use the first one if finds.
Geocode (lat, long)
IATA Code
ICAO Code
Place ID
Postal Key

These options are listed here:
https://docs.google.com/document/d/1_Zte7-SdOjnzBttb1-Y9e0Wgl0_3tah9dSwXUyEA3-c/

Examples:
geocode = "33.74,-84.39"
iataCode = DEN
icaoCode = KDEN
placeid = 327145917e06d09373dd2760425a88622a62d248fd97550eb4883737d8d1173b
postalKey = 81657:US