Add missing quote import for Python 2.x

When running under Python 2.x, this import is missing and we get an
error when running anything with `etherdump pull`.

etherdump/commands/pull.py

@@ -6,7 +6,7 @@ from datetime import datetime
 try:
     # python2
     from urllib2 import urlopen, URLError, HTTPError
-    from urllib import urlencode
+    from urllib import urlencode, quote
 except ImportError:
     # python3
     from urllib.parse import urlencode, quote