More readline functionality

Implements some of the readline commands that I use constantly (e.g. I use C-p instead of up arrow, and it hits me *every* line >.<)

* **ctrlp** - scroll back through history (same as up arrow)
* **ctrln** - scroll forward through history (same as down arrow)
* **ctrlk** - kill to end of line
* **ctrlu** - kill to beginning of line
* **ctrly** - yank previously killed text

For more details, see commit messages, esp 83c76d1f2bf6af928e3cd625d79ab526ccd071b5