+ Added caca_get_dithering_name().
  * src/bitmap.c:
    + Created a new dithering method with an 8x8 ordered matrix.
    + Replaced the char list with a string for better readability.
    + Dithering functions now return a value between 0 and 255.
  * examples/demo.c examples/view.c:
    + Adapted to use caca_get_dithering_name().