display() sends data for pages 0-5, clear(ALL) sends zeros for pages 0-7

I noticed this when I was working with the library - `display()` outer loop for sending data is `for (i = 0; i < 6; i++)` but `clear(uint8_t mode)` (and `clear(uint8_t mode, uint8_t c)`) outer loop for sending zeros/values is `for (int i = 0; i < 8; i++)`
Note that display is looping through the range 0...5, but clear is looping through the range 0...7.