Updated bash setup, bashrc, vimrc.

Bash setup:
  - fixed an error introduced when I was messing around with changes.
  - still very bare bones.

dot.bashrc:
  - changed the prompt to use octal colours when showing exit status,
    since OS X (Mavericks, at least) didn't like the notation previously
    used.

dot.vimrc:
  - added force for syntax highlighting, due to OS X not having it on
    by default.