.bashrc: Modify $PS1 and $PS2

The old PS1 was definitely nice -- it did the job of highlighting where
I was supposed to type text. But it was also a bit unwieldy, and very
difficult to modify for things like adding Git repo information or
virtualenv info. I'd like something I can split into different parts so
I can more easily customize the prompt in different scenarios.
.vimrc: Remove key nav remap