Refactoring: add subclasses for linear and logistic policies

[Kurorororo]

fix #66

[usaito]

@Kurorororo

Thanks! I think self.reward_lists and self.context_lists have to be initialized in BaseLogisticPolicy

self.reward_lists = [[] for _ in np.arange(self.n_actions)]
self.context_lists = [[] for _ in np.arange(self.n_actions)]

the other parts LGTM!

[Kurorororo]

@usaito
They are initialized in BaseContextualPolicy, a superclass of BaseLogisticPolicy.

zr-obp/obp/policy/base.py

Lines 153 to 154 in dac1ec0

	self.reward_lists = [[] for _ in np.arange(self.n_actions)]
	self.context_lists = [[] for _ in np.arange(self.n_actions)]

[usaito]

@Kurorororo Got it, thanks!