RENDER-STACK now renders lists properly.
Variable name repl-input -> input.
There's only one of it, and it's not really a REPL.
Higher-order functions now FILTH-PUSH instead of returning.
Adds INPUT-HISTORY.
Tweaks RENDER-LIST.
Also, offsetting the x coord is no longer necessary in RENDER-STACK.
Adds LOAD-FILE, which evaluates FTH files.
Paren-blocks are now comments.
Paren-blocks have their own color.