README: Change structure a bit

These scripts will need to be moved to a scripts/ directory anyway, so
might as well have it be a submodule of another repository.

README.md

@@ -19,12 +19,16 @@ ptouch.pl uses the following modules:
 
 ## How to use
 
-You'll need to create the following directories:
+Make an initial directory with the following structure:
 
-* posts/
-* pages/ - Templated pages
-* assets/ - Static assets
-* templates/ - Templates you can call with `include_tmpl`
+* site_dir/
+  * posts/
+  * pages/ - Templated pages
+  * assets/ - Static assets
+  * templates/ - Templates you can call with `include_tmpl`
+
+Either clone this repository to site_dir/scripts/, or add this
+repository as a git submodule.
 
 To make a new post, create a file with the following format in the
 posts/ folder: