v2.0.0

Every seed's output changes from 1.x.

• Dry spells: a semi-Markov rain chain; the year's longest dry spell is now 3% short of the stations' (6% in 1.x).
• The wettest days: Weibull amounts tied to how deep in the rain the day is; the 95th percentile is no longer light.
• Fronts: a day's temperature follows the rain on it and around it, warm before the rain and cold after.
• New fields: snow_depth (snow lies, melts in a thaw and settles as it ages), gust, fog, solar_radiation, and the fog and drizzle conditions. Sunshine is fitted on CRU sunshine records.
• One world per seed: weather_request::spatial, on by default, makes nearby places share their weather, with correlations that fall with distance as between weather stations. spatial = false gives each cell its own weather, as in 1.x.
• JSON always has "units".

A single day costs about 4x 1.x at a random place, more in winter in cold places (the snow season so far is simulated); a year's series about 1.5x. See Data and Method for the fits, the validation and the known shortfalls.