rearranged documentation, added basic troubleshooting guide

docs/staging.md

@@ -0,0 +1,15 @@
+# Staging
+
+Let’s Encrypt has stringent rate limits in place during the public beta period.
+
+If you start testing using the production endpoint (which is the default),
+you will quickly hit these limits and find yourself locked out.
+
+To avoid this, please set the CA property to the Let’s Encrypt staging server URL in your `config.sh` file:
+
+```bash
+CA="https://acme-staging.api.letsencrypt.org/directory"
+```
+
+Please keep in mind that at the time of writing this letsencrypt.sh doesn't have support for registration management,
+so if you change CA you'll have to move your `private_key.pem` (and, if you care, `private_key.json`) out of the way.