moved `pwnlib.replacements.time.sleep()` to `pwnlib.replacements.sleep()`
added `replacements` to __init__.py
added `pwnlib.replacements.*` to `pwn.toplevel`
updated docstrings in `pwnlib.replacements`.
added docs for `pwnlib.replacements`.
added docstrings for `pwnlib.rop`.
addde `pwnlib.rop` to docs.