Update Adafruit_SSD1306.cpp

In functions startscrollleft(uint8_t start, uint8_t stop) and startscrollright(uint8_t start, uint8_t stop),
E[7:0] : Dummy byte was set to 0x01 instead of 0x00 (Datasheet page 28).
The first pixel column was not scrolled.
Merge pull request #3 from ghost/patch-1

Hotizontal scrolling update Adafruit_SSD1306.cpp