fixed #164 - added a note about backing .emacs and .emacs.d

README.md

@@ -50,6 +50,10 @@ To change the source repository:
 https://github.com/bbatsov/prelude/raw/master/utils/installer.sh
 | sh`
 
+Note that the installer will back up any existing `.emacs` file or
+`.emacs.d` since it will unpack Prelude's code in `.emacs.d`. If
+you're doing a manual install make sure you don't have a `.emacs` file
+or back up your existing `.emacs.d` directory manually.
 
 ## Would you like to know more?