Save params

[TomorrowIsAnOtherDay]

This PR resolves #106 :

1. add save() and restore() APIs for parl.Agent
2. add unit test for the new feature.

Usage:

>> agent = AtariAgent()
>> agent.save('./model.ckpt')
>> agent.restore('./model.ckpt')
>> another_agent =  AtariAgent()
>> another_agent.restore('./model.ckpt')

[zienn]

File "/home/tianqi/Distributed-MultiAgentRL/train.py", line 293, in display
agent.restore('./model.ckpt')
File "/home/tianqi/anaconda3/lib/python3.6/site-packages/parl/core/fluid/agent.py", line 221, in restore
filename=filename)
File "/home/tianqi/anaconda3/lib/python3.6/site-packages/paddle/fluid/io.py", line 798, in load_params
filename=filename)
File "/home/tianqi/anaconda3/lib/python3.6/site-packages/paddle/fluid/io.py", line 675, in load_vars
raise TypeError("program's type should be Program")
TypeError: program's type should be Program

[TomorrowIsAnOtherDay]

@Termset Could you please open an issue and describe the details of your code?

[zienn]

@Termset Could you please open an issue and describe the details of your code?

ok