Update community links for Discussion

CONTRIBUTING.md

@@ -52,7 +52,6 @@ If running into any compiling issue
 >1. For proto/thrift errors, run `git submodule update --init --recursive` to fix  
 >2. Make sure you upgrade to the latest stable version of Golang.
 >3. Check if this document is outdated by comparing with the building steps in [Dockerfile](https://github.com/uber/cadence/blob/master/Dockerfile)
-* Database. The default setup of Cadence depends on Cassandra. Before running the Cadence or tests you must have `cassandra` dependency(or equivalent database in the below notes)
 
 ### 2. Setup Dependency
 NOTE: you may skip this section if you have installed the dependencies in any other ways, for example, using homebrew.

README.md

@@ -55,10 +55,15 @@ Visit [cadenceworkflow.io](https://cadenceworkflow.io) for documentation.
 
 Join us in [Cadence Docs](https://github.com/uber/cadence-docs) project. Raise an Issue or Pull Request there.
 
-## Getting Help
+## Community 
+* [Github Discussion](https://github.com/uber/cadence/discussions)
+  * Best for Q&A, support/help, general discusion, and annoucement 
 * [StackOverflow](https://stackoverflow.com/questions/tagged/cadence-workflow)
+  * Best for Q&A and general discusion
 * [Github Issues](https://github.com/uber/cadence/issues)
+  * Best for reporting bugs and feature requests
 * [Slack](http://t.uber.com/cadence-slack)
+  * Best for contributing/development discussion 
 
 ## Contributing