wifi status fix, added applesmc module

fixed wifi.py issue where regex match fails when no interface is found (at some point during sleep/resume process).  
Also added icon/color changes to wifi icon to indicate different states:
no interface (gray, empty icon)
ssid but no ip (red, 'full' icon)
ssid with ip   (green, 'full' icon)

Also added applesmc.py, module for reporting fan and temperature for apple laptop sensors.