Correct date-range for daily downloads

[steffilazerte]

Correct date-range for daily downloads. Fixes #69
And assorted bugfixes/cleanup

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@deaaa30). Click here to learn what that means.
The diff coverage is 91.3%.

@@            Coverage Diff            @@
##             master      #73   +/-   ##
=========================================
  Coverage          ?   78.73%           
=========================================
  Files             ?        5           
  Lines             ?      583           
  Branches          ?        0           
=========================================
  Hits              ?      459           
  Misses            ?      124           
  Partials          ?        0

Impacted Files	Coverage Δ
R/weather.R	97.6% <91.3%> (ø)

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