remove unused import in controllers/security

[fredj]

simplejson is imported but not used, patch:

Index: mapfish/controllers/security.py
===================================================================
--- mapfish/controllers/security.py	(revision 3601)
+++ mapfish/controllers/security.py	(working copy)
@@ -6,7 +6,6 @@
 from authkit.authorize.pylons_adaptors import authorize, authorized
 from authkit.permissions import ValidAuthKitUser
 from authkit.authorize import NotAuthorizedError
-import simplejson
 
 import sys
 import os

[fredj]

(In [3602]) remove unused import. r=elemoine (closes #595)