Update README.md

Author: YangRui2015

README.md

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 # Sparse-Reward-Algorithms
 
-Implement many Sparse Reward algorithms in Gym Fetch environment
+We implemented many classes of Sparse Reward algorithms in Gym Fetch environment including Reward Shaping, Imitation Learning, Curriculum Learning, Hindsight Experience Replay, Curiosity-Driven Exploration, Hierachical Reinforcement Learning. This work is for better understanding of sparse reward algorithms.
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+Our code is based on https://github.com/andrew-j-levy/Hierarchical-Actor-Critc-HAC- and we have changed a lot on code simplif ication and content richness.