Documentation fixes - Githubissues

This pull request

fixes the documentation for accepted values for Weather.wind's unit parameter, which accepts 'km_hour', not 'kilometers_hour'
adds some missing single quotation marks in the documentation for Weather.reference_time, Weather.sunset_time, and Weather.sunrise_time
updates the reference link for OWM weather codes and icons in the documentation for Weather; http://bugs.openweathermap.org/projects/api/wiki/Weather_Condition_Codes now errors

csparpa / pyowm