added support for 96x16 (8.4") OLED display

Hey guys, here is my code for the 96x16 class. It works fine with the shape.py example.
Not sure about line #L337-339 because there is some difference between class SSD1306_128_64 and SSD1306_128_32 at this point and I don't understand what it is good for. So I just copied the 128_32 version.