Move request counter into State model

fbchat/_state.py

@@ -12,12 +12,15 @@ class State(object):
 
     fb_dtsg = attr.ib(None)
     _revision = attr.ib(None)
+    _counter = attr.ib(0)
 
     def get_params(self):
         if self.fb_dtsg is None:
             return {}
+        self._counter += 1  # TODO: Make this operation atomic / thread-safe
         return {
             "__a": 1,
+            "__req": _util.str_base(self._counter, 36),
             "__rev": self._revision,
             "fb_dtsg": self.fb_dtsg,
         }