Email source code cleanups. Use the header variable returned from flanker to extract the sender and the subject. Remove unsed scanimage usage via sh.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/sources/classes.py

@@ -1,7 +1,6 @@
 from __future__ import unicode_literals
 
 import base64
-from io import BytesIO
 import os
 import time
 import urllib