TooTallNate/superagent-proxy — pull request #4 by kinua (2013-11-18 03:07:17+00:00)
Title: return this if the proxy uri is null

Sometimes production env is different from development env.

In production config
```
config = {
proxy: null
};
```

In development config
```
config = {
proxy: 'http://10.1.10.200:3128'
};
```

It is nice to have this api syntax.
```
var config = require('config');
request
.get('http://www.google.com')
.proxy(config.proxy)
.end(function (res) {});
```

otherwise, i need to write something like this

```
var config = require('config');
req = request.get('http://www.google.com')
if (config.proxy) {
req = req.proxy(config.proxy);
}
req.end(function (res) {});
```

more ugly