Update README.md

Add not about shapely/geos

README.md

@@ -60,6 +60,13 @@ To switch redis on you'll need to install it locally. On a OSX we've used brew f
 
         REDIS_ENABLED = True
         
+### Other dependencies
+
+Shapely, a subdependency required by notifications-utils, will fail to install unless you install its dependencies
+
+```
+brew install geos
+```
 
 ##  To run the application