Revert "Support trading on margin"

This reverts commit 681bcee

Author: sinall

shipane_sdk/client.py

@@ -119,14 +119,6 @@ def sell(self, client=None, timeout=None, **kwargs):
         kwargs['action'] = 'SELL'
         return self.__execute(client, timeout, **kwargs)
 
-    def buy_on_margin(self, client=None, timeout=None, **kwargs):
-        kwargs['action'] = 'BUY_ON_MARGIN'
-        return self.__execute(client, timeout, **kwargs)
-
-    def sell_then_repay(self, client=None, timeout=None, **kwargs):
-        kwargs['action'] = 'SELL_THEN_REPAY'
-        return self.__execute(client, timeout, **kwargs)
-
     def ipo(self, client=None, timeout=None, **kwargs):
         kwargs['action'] = 'IPO'
         return self.__execute(client, timeout, **kwargs)