request hangs if joi-router used together with a body parser
NodeJS: 8.6.0
npm: 5.2.0
OS: Max OS X 10.12.2
koa: 2.4.1
koa-joi-router: 5.0.0
koa-bodyparser: 4.2.0
koa-body: 2.5.0

For the following app:
```js
const koa = require('koa');
const router = require('koa-joi-router');
const bodyParser = require('koa-bodyparser');

const public = router();

public.route({
  method: 'post',
  path: '/foo',
  validate: {
    type: 'json',
  },
  handler: async (ctx) => {
    ctx.status = 201;
  }
});

const app = new koa();
app.use(bodyParser());
app.use(public.middleware());
app.listen(2999);
```
the request hangs. The same if `koa-body` used instead if `koa-bodyparser`.

I need a koa body parser to be able to use request body in the middlewares.