updated install page to have better installation instructions

doc-src/Gemfile.lock

@@ -8,7 +8,7 @@ GIT
 PATH
   remote: ..
   specs:
-    compass (0.11.beta.5.428e5b5)
+    compass (0.11.beta.5.04ab1e3)
       chunky_png (~> 1.1.0)
       sass (>= 3.1.0.alpha.249)
 

doc-src/content/install.haml

@@ -5,9 +5,19 @@ body_id: install
 ---
 - content_for :javascripts do
   %script(src="/javascripts/install.js")
+  
+%h2 Installing Ruby  
 %p
   Compass runs on any computer that has
   <a href="http://www.ruby-lang.org/en/downloads/">ruby installed</a>.
+%p
+  For more advanced users you may want to install
+  <a href="http://rvm.beginrescueend.com/rvm/install/">rvm</a>.
+
+%h2 Setting up the ruby environment
+%ol
+  %li <code>$ gem update --system</code>
+  %li <code>$ gem install compass</code>
 
 %h2 Tell us about your project and we'll help you get it set up:
 %blockquote.madlib.customizable<