Notebook eRL_demo_StockTrading.ipynb doen't work

Hi,

It seems that notebook eRL_demo_StockTrading.ipynb is deprecated and broken. It throughs the following error:

> Traceback (most recent call last):
File "/usr/lib/python3.7/multiprocessing/process.py", line 297, in _bootstrap
self.run()
File "/usr/lib/python3.7/multiprocessing/process.py", line 99, in run
self._target(*self._args, **self._kwargs)
File "/usr/local/lib/python3.7/dist-packages/elegantrl/run.py", line 340, in run
agent.states = [env.reset(), ]
File "/usr/local/lib/python3.7/dist-packages/elegantrl/envs/FinRL/StockTrading.py", line 47, in reset
self.amount = self.initial_capital * rd.uniform(0.95, 1.05) - (self.stocks * price).sum()
ValueError: operands could not be broadcast together with shapes (74,) (73,)