Documentation update

[Gavin Sinclair]

Hi folks,

I thought it might be time to update the documentation for this
project, and get everything a user needs into the homepage
(http://vim-ruby.rubyforge.org).  At the same time, I'd review the
wiki pages.

So can people suggest what should go in the "one consolidated
document"?  Pretend I know nothing about the project and suggest
_anything_.

Thanks,
Gavin