readme tweaks

Readme.md

@@ -8,11 +8,23 @@ Django settings.py
 ------------------
 
 Sets up a db for every ENV ${NAME}_URL => postgres:// var:
+
     DATABASES["DATABASE"]
     DATABASES["SHARED_DATABASE"]
     DATABASES["HEROKU_POSTGRESQL_ONYX"]
 
 Aliases DATABASE_URL to default database:
+
     DATABASES["default"] = DATABASES["DATABASE"]
 
 Injected right after DATABASES = {...}
+
+Hooks
+-----
+
+Uses a Makefile for user-controlled hooks into slug compilation.
+Target `environment` will be evald in the build script, allowing
+custom exports. PIP_OPTS is passed to pip if set.
+
+    environment:
+    	export PIP_OPTS=--upgrade