Add comma

Author: edwardcwang

README.md

@@ -180,6 +180,6 @@ Some useful typeclasses:
 
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-This code is maintained by [Chick](https://github.com/chick) [Angie](https://github.com/shunshou) and [Paul](https://github.com/grebe). Let us know if you have any questions/feedback!
+This code is maintained by [Chick](https://github.com/chick), [Angie](https://github.com/shunshou) and [Paul](https://github.com/grebe). Let us know if you have any questions/feedback!
 
 Copyright (c) 2015 - 2016 The Regents of the University of California. Released under the Modified (3-clause) BSD license.