Added docs for options hash to optimist.

I had to dig a bit to figure out how to get options working on argv,
thought I'd save others the time.

README.md

@@ -157,13 +157,20 @@ A simple in-memory storage engine that stores a nested JSON representation of th
 ```
 
 ### Argv
-Responsible for loading the values parsed from `process.argv` by `optimist` into the configuration hierarchy.
+Responsible for loading the values parsed from `process.argv` by `optimist` into the configuration hierarchy. See the [optimist option docs](https://github.com/substack/node-optimist/#optionskey-opt) for more on the option format.
 
 ``` js
   //
   // Can optionally also be an object literal to pass to `optimist`.
   //
-  nconf.argv(options);  
+  nconf.argv({
+    "x": {
+      alias: 'example',
+      describe: 'Example description for usage generation',
+      demand: true,
+      default: 'some-value'
+    }
+  });
 ```
 
 ### Env