Fix missing gitter links (#519)

Author: mayurkale22

packages/opencensus-nodejs-base/README.md

@@ -50,3 +50,11 @@ tracing.tracer.startRootSpan(rootSpanOptions, (rootSpan) => {
 ### Tracing Options
 
  See the `@opencensus/nodejs` package for the full API documentation.
+
+## Useful links
+- For more information on OpenCensus, visit: <https://opencensus.io/>
+- To checkout the OpenCensus for Node.js, visit: <https://github.com/census-instrumentation/opencensus-node>
+- For help or feedback on this project, join us on [gitter](https://gitter.im/census-instrumentation/Lobby)
+
+[gitter-image]: https://badges.gitter.im/census-instrumentation/lobby.svg
+[gitter-url]: https://gitter.im/census-instrumentation/lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge