update of api docstrings across coach and tutorials [WIP] (#91)

* updating the documentation website
* adding the built docs
* update of api docstrings across coach and tutorials 0-2
* added some missing api documentation
* New Sphinx based documentation

docs_raw/source/components/agents/policy_optimization/hac.rst

@@ -0,0 +1,24 @@
+Hierarchical Actor Critic
+=========================
+
+**Actions space:** Continuous
+
+**References:** `Hierarchical Reinforcement Learning with Hindsight <https://arxiv.org/abs/1805.08180>`_
+
+Network Structure
+-----------------
+
+.. image:: /_static/img/design_imgs/ddpg.png
+   :align: center
+
+Algorithm Description
+---------------------
+Choosing an action
+++++++++++++++++++
+
+Pass the current states through the actor network, and get an action mean vector :math:`\mu`.
+While in training phase, use a continuous exploration policy, such as the Ornstein-Uhlenbeck process,
+to add exploration noise to the action. When testing, use the mean vector :math:`\mu` as-is.
+
+Training the network
+++++++++++++++++++++