Add ability to display upcoming weekly forecast

Hey Frederic,

I added the ability to display the forecast for the upcoming week from this part of the API:

http://api.openweathermap.org/data/2.5/forecast/daily?q=Moscow,RU

By adding `forecast:true` to the config file or invoking from the command line with `./ansiweather forecast`

Hope you like it.

Cheers,
Mike