Integers, Characters, and I/O (updated)

This release adds integers, characters and I/O, see the README file for details.

S/K/I/B/C and Y

This version adds a direct implementation of the Y combinator.

Pure S/K/I/B/C.

This version marks completion of the pure S/K/I/B/C only version of the system. If you want S/K/I/B/C and nothing else, this is it.