+ Moved ee_putstr() and ee_putchar() in here.
  * libee/ee.h:
    + Got rid of ee_goto().
    + Moved <slang.h> or <curses.h> into libee.
  * Replaced ee_goto()/ee_putstr() pairs with ee_putstr().
  * Ditto for ee_putchar().

+ Implemented ee_fill_triangle().
  * test/demo.c:
    + Triangle demo.