updates readme, documenting USR2

README.rdoc

@@ -68,6 +68,8 @@ Initially, you may find that a few files don't reload automatically.  This is be
 
 It will output a lot of stuff.  At the top you'll find a summary of all project files loaded.  Down below, the stack trace for each file (how it got loaded).  Spork hooks into Rails and does some magic (TM) to prevent ApplicationController observers, etc from pre-loading.  Similar hooks for other ruby frameworks may come as support demands.
 
+Some project changes will require a spork restart, and you shouldn't expect them to not (IE: modifying your project gem dependencies or core application config).  Any file that is loaded during Spork start-up will be cached until Spork is restarted.  You can restart spork by sending a USR2 signal to the server process.  This could be automated with a gem such as Kicker (https://github.com/alloy/kicker).  Since a native hook is required for each operating system to efficiently watch for filesystem changes, automatic restarting has not been built into Spork.
+
 You may find this wiki page useful for common ways to battle a variety of common pre-loading issues: http://github.com/timcharper/spork/wiki/Spork.trap_method-Jujutsu
 
 == Running specs over Spork