Merge pull request #174 from milvus-io/master

Update README.md

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README.md

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 ## What is Milvus
 
-Milvus is an open source similarity search engine for massive-scale feature vectors. Built with heterogeneous computing architecture for the best cost efficiency. Searches over billion-scale vectors take only milliseconds with minimum computing resources.
+Milvus is the world's fastest similarity search engine for massive-scale feature vectors. Built with heterogeneous computing architecture for the best cost efficiency. Searches over billion-scale vectors take only milliseconds with minimum computing resources.
 
 For more detailed introduction of Milvus and its architecture, see [Milvus overview](https://www.milvus.io/docs/en/aboutmilvus/overview/).