text: Title: New style streaming route handler improvements
  Body: **Is your feature request related to a problem? Please describe.**
  The new streaming API allows streaming responses in the route handler without having to use a callback:
  
  ```python
  @app.route("/")
  async def test(request):
      response = await request.respond(content_type="text/csv")
      await response.send("foo,")
      await response.send("bar")
      await response.send("", True)
      return response
  ```
  
  **Describe the solution you'd like**
  A simpler method to closing the stream before returning in place of `await response.send("", True)`
  
  ```python
  await response.eof()
  ```
  
  Under the hood, `eof` should simply just be a convenience call to `send("", True)`.