self.signal_features[0] and self.signal_features[-1] are never be used

[lbgitjp]

in the class TradingEnv, self.signal_features[0] and self.signal_features[-1] are never be used.

1. below code will skip self.signal_features[0]: https://github.com/AminHP/gym-anytrading/blob/296bae49e77d08a7c7349b542cdd00ea7ca23af0/gym_anytrading/envs/trading_env.py#L104-L105

I think it should be changed to:

def _get_observation(self):
    return self.signal_features[(self._current_tick-self.window_size):self._current_tick]

2. below code will skip self.signal_features[-1]: https://github.com/AminHP/gym-anytrading/blob/296bae49e77d08a7c7349b542cdd00ea7ca23af0/gym_anytrading/envs/trading_env.py#L75-L76 I think it should be changed to:

   if self._current_tick == self._end_tick+ 1:
       self._done = True

thanks!