优化工单模块，增加企微模块

sg_wechat_enterprise/we_api/session/memorystorage.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+from __future__ import absolute_import, unicode_literals
+from wechatpy.session import SessionStorage
+
+
+class MemoryStorage(SessionStorage):
+
+    def __init__(self):
+        self._data = {}
+
+    def get(self, key, default=None):
+        return self._data.get(key, default)
+
+    def set(self, key, value, ttl=None):
+        if value is None:
+            return
+        self._data[key] = value
+
+    def delete(self, key):
+        self._data.pop(key, None)