Allow printing of degree symbol in summaries

Without utf-8 encoding, the print-calls cause a unicode encode error:

    Traceback (most recent call last):
      File "simpleWeather.py", line 210, in <module>
        display_weekly_forecast()
      File "simpleWeather.py", line 175, in display_weekly_forecast
        print("Forecast for the coming week: {0}".format(week_summary))
    UnicodeEncodeError: 'ascii' codec can't encode character u'\xb0' in
position 69: ordinal not in range(128)