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.
Separate StubConfs between different tests

Stub for @conf was sharing the same class between
test/disp_referrer_test.rb test/weather_test.rb.
Typo is also fixed, from Stab to Stub.
Merge pull request #405 from zunda/weather_aviatoinweather_gov-pr

Update source URL for weather information