note that rails won't autoload the gem

Author: malakai97

README.md

@@ -26,6 +26,8 @@ Or install it yourself as:
 ## Usage
 
 ```ruby
+  require 'pairtree' # You'll need to do this in rails, as it won't find it automatically.
+
   # Initiate a tree
   pairtree = Pairtree.at('./data', :prefix => 'pfx:', :create => true)