Add a testing module for backtesting

[oulianov]

Add a basic implementation to do backtesting with an agent with the following syntax

# phospho_test.py
phospho_test = phospho.PhosphoTest()

 @phospho_test.test
 def test_santa(**inputs):
     agent = Agent()
     return agent.answer(**inputs)
     
 phospho_test.run()

python phospho_test.py

[oulianov]

To debug : pandas mode