Opening configuration up for extension:

Added a gvimrc file, which only contains a source ~/.gvimrc-ext.
Added a source ~/.vimrc-ext to the .vimrc
Added my gvimrc-ext and vimrc-ext as examples

Made a change that might make it easier for people to try out your .vim without clobbering their existing stuf... oh, shoot, should've made a change to the install instructions...