Adding vim colorschemes; vimrc updates

Adding the railscasts and shobogenzo vim colorschemes.  Changing default
colorscheme to railscasts.

Turning on relativenumber by default (in command mode).

Making vim use relativenumber in command mode, and number in insert
mode.

Removing a bunch of comment-only lines from .vimrc - looks like a hold
over from an older version of vim that might have had some bugs in the
config parsing routines.  <shrug>