Update source URL for weather information

NOAA changed URL from
http://weather.noaa.gov/weather/current/#{station_id}.html
to
http://www.aviationweather.gov/adds/metars/?station_ids=#{station_id}&std_trans=translated&chk_metars=on&hoursStr=most+recent+only
accordingly, URL is translalted each time the plugin treis to
fetch weather and updated permanently when the plugin is
configured.

The format of the table in the HTML page has also been updated.

Indents in test/weather_test.rb are fixed.

これで https://github.com/tdiary/tdiary-core/issues/155 を閉じられるはずです