Ditch install advice

I'm going to stop providing it on all but my most popular plugins, on
account of the fact there are a dozen different methods, and people tend
to know how to use their own.

README.markdown

@@ -36,18 +36,6 @@ reflect the nearest `.ruby-version` file.
 
 [vim-ruby]: https://github.com/vim-ruby/vim-ruby
 
-## Installation
-
-If you don't have a preferred installation method, I recommend
-installing [pathogen.vim](https://github.com/tpope/vim-pathogen), and
-then simply copy and paste:
-
-    cd ~/.vim/bundle
-    git clone git://github.com/tpope/vim-rvm.git
-
-Once help tags have been generated, you can view the manual with
-`:help rvm`.
-
 ## FAQ
 
 > RVM doesn't work in my Vim.