Add -p option on mkdir command

Else the `mkdir -p ${deploy_to}` fails on my system because `/var/www/` did not exist.

documentation/getting-started/authentication-and-authorisation/index.markdown

@@ -322,7 +322,7 @@ access that you may or may not need depending how well your servers are setup:
     # Capistrano will use /var/www/....... where ... is the value set in
     # :application, you can override this by setting the ':deploy_to' variable
     root@remote $ deploy_to=/var/www/rails3-bootstrap-devise-cancan-demo
-    root@remote $ mkdir ${deploy_to}
+    root@remote $ mkdir -p ${deploy_to}
     root@remote $ chown deploy:deploy ${deploy_to}
     root@remote $ umask 0002
     root@remote $ chmod g+s ${deploy_to}