Revert "Skeleton change: read from stdin as per lab doc."

This reverts commit 5f3fc716d873b0d98ee659b7bb90f904b1c4478b.
Merge branch 'master' of https://github.com/aaronbloomfield/pdr
Merge branch 'master' of https://github.com/cceckman/pdr
Incorrect opcodes in IBCM chapter

The IBCM chapter incorrectly gave shift operations an opcode of 1 in a
couple of cases. According to the slides & elsewhere in the chapter,
shift instructions have an opcode of 2.

(This commit does not include changes related to issue #21.)
Merge pull request #22 from cceckman/master

Incorrect opcodes in IBCM chapter