end() doesn't work if stream is in a paused state

I noticed this piping memorystream to something else. I.e., this was totally busted:

```
var ms = new MemoryStream();

ms.pause();


call_something_that_sets_up_a_pipe_async(ms);

process.nextTick(function () {
    ms.end('foo');
});
```

Where that function (in my case) was setting up a pipe _after_ it had gotten a node http client established. So the `end('data')` was long gone, and the module never emitted.