SteamAuthenticator: add revocation_code param to remove() method

fix #262

steam/guard.py

@@ -207,9 +207,12 @@ class SteamAuthenticator(object):
 
         self.steam_time_offset = int(resp['server_time']) - time()
 
-    def remove(self):
+    def remove(self, revocation_code=None):
         """Remove authenticator
 
+        :param revocation_code: revocation code for account (e.g. R12345)
+        :type  revocation_code: str
+
         .. note::
             After removing authenticator Steam Guard will be set to email codes
 
@@ -225,7 +228,7 @@ class SteamAuthenticator(object):
 
         resp = self._send_request('RemoveAuthenticator', {
             'steamid': self.backend.steam_id,
-            'revocation_code': self.revocation_code,
+            'revocation_code': revocation_code if revocation_code else self.revocation_code,
             'steamguard_scheme': 1,
         })