Support for body-parser module (req.body)

Hello, thanks for the lib.

I was having some trouble getting the data to come through using the new express and bodyParser style, because it puts the parsed result into `request.body` instead of `request.body.payload`.  This is a patch that fixes it for me.

example:

```js
var express = require('express');
var bodyParser = require('body-parser');
var app = express();
app.use(bodyParser.json());
app.use(cgh(..));
```

:beers: