Fetch weather information from WeatherBug for one city and display it in a fragment.

Added
 - app permission for access to internet in AndroidManifest.xml
 - SingleForecastFragment that sets up a fragment to display weather
 forecast information
 -- newInstance that fires a new fragment instance
 -- onCreate (instance creation)
 -- onActivityCreated
 -- onCreateView
 -- interface ForecastListener that is to be triggered when
 ReadForecastTask finishes
 - forecast_fragment.xml as layout for SingleForecastFragment
 - URL prefix for WeatherBug web API in string.xml
 - ReadForecastTask (extends AsyncTask) that contacts WeatherBug web API
 and asks for an hourly forecast for a zip code
 - code to replace forecast_replacer with a SingleForecastFragment