Typo: resond -> respond

Author: Andrew Ash <andrew@andrewash.com>

Closes #743 from ash211/patch-4 and squashes the following commits:

c959f3b [Andrew Ash] Typo: resond -> respond

(cherry picked from commit a5150d199ca97ab2992bc2bb221a3ebf3d3450ba)
Signed-off-by: Reynold Xin <rxin@apache.org>