Fixing output for windspeedmph

Adding line of code at 178:

    windspeedmph = currentSpeed;//update global variable for windspeed when using the printWeather() function

and added comment to line 227 to explain why the calculation was commented out:

    //windspeedmph = get_wind_speed(); //This is calculated in the main loop on line 179

to fix this issue => https://github.com/sparkfun/Weather_Shield/issues/24