fix module exports

fixes error

```js
const Ws = require('pull-ws/client')

Ws.connect(...)
// ! Uncaught TypeError: Ws.connect is not a function
```

Author: ahdinosaur

client.js

@@ -29,4 +29,4 @@ module.exports = function (addr, opts) {
   return stream
 }
 
-exports.connect = module.exports
+module.exports.connect = module.exports

index.js

@@ -1,4 +1,4 @@
-exports = module.exports = require('./duplex')
+var exports = module.exports = require('./duplex')
 
 exports.source = require('./source');
 exports.sink = require('./sink');