stream_tags hangs when used with Stream.take

Hello! Thanks for making sweet_xml!

The following code hangs:

```elixir
"<feed></feed>" |> stream_tags(:feed) |> Stream.take(1) |> Enum.to_list
```

... but removing the Stream.take lets the code run to completion as expected:

```elixir
"<feed></feed>" |> stream_tags(:feed) |> Enum.to_list
```