Add info for setting the API key and example message.

README.md

@@ -18,11 +18,15 @@ Then add **hubot-esv** to your `external-scripts.json`:
 ]
 ```
 
+This plugin requires an API key from api.esv.org.  Set this 
+as HUBOT_ESV_API_KEY in the hubot environment.
+An API key can be obtained at https://api.esv.org/account/create-application/
+
 ## Sample Interaction
 
 ```
-user1>> hubot hello
-hubot>> hello!
+user1>> hubot esv John 3:16
+hubot>> [16] “For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. (ESV)
 ```
 
 ## NPM Module