Calling a service with no return body do not executes end()

Hi. Given an API for deleting objects, it returns `202 Accepted` and no content in the body.

When using unirest for calling it this way:

```
unirest
.post("/deleteByIds")
.headers({
"Content-Type": "application/json"
})
.send(ids)
.end(function (res) {
//code handling - never called
});
}
```

The `end()` function is never called back, however the service has already responded 202 with no body. Tested using `unirest-nodejs` version `0.4.2`.

Could this be related to PR #74 ?

Start at the request chain's .end() callback handling in unirest-nodejs and compare the behavior with PR #74. Reproduce the 202 Accepted response with no body, then verify that the callback is invoked and the response is handled correctly.

Written by the indexing model from the issue text.