self.__chips now contains the list of rgbtuple values for the
    chips named i - 1 (Tkinter counts from 1, we count from zero).
    The chip number was just the index + 1.  This means color lookup
    need not do an itemcget(), it can just index into __chips.

    instead of calling __canvas.itemconfigure(), we glom up a huge Tcl
    script and call tk.eval() directly.  Actually we do many appends
    to a Python list, then string.join() them together into one huge
    string.  This reduces the overhead of Tkinter but making one fast
    call to Tcl.