Changing gitter link to slack invite link
Closes from shirshanka/readmeslack
[![Documentation Status](https://readthedocs.org/projects/gobblin/badge/?version=latest)](https://gobblin.readthedocs.org/en/latest/?badge=latest)
[![Maven Central](https://maven-badges.herokuapp.com/maven-central/org.apache.gobblin/gobblin-api/badge.svg)](https://search.maven.org/search?q=g:org.apache.gobblin)
[![Stack Overflow](http://img.shields.io/:stack%20overflow-gobblin-brightgreen.svg)](http://stackoverflow.com/questions/tagged/gobblin)
-[![Gitter](https://img.shields.io/gitter/room/gobblin/Lobby)](https://gitter.im/gobblin/Lobby/)
+[![Get on Slack](https://img.shields.io/badge/slack-join-orange.svg)](https://join.slack.com/t/apache-gobblin/shared_invite/zt-hkwu51id-aVxL3bvtLdi778YHFV1b6A)
[![codecov.io](https://codecov.io/github/apache/incubator-gobblin/branch/master/graph/badge.svg)](https://codecov.io/github/apache/incubator-gobblin)
Apache Gobblin is a universal data ingestion framework for extracting, transforming, and loading large volume of data from a variety of data sources: databases, rest APIs, FTP/SFTP servers, filers, etc., onto Hadoop.
@@ -52,8 +52,8 @@ The distribution will be created in build/gobblin-distribution/distributions dir
* [Gobblin documentation](http://gobblin.readthedocs.org/en/latest/)
* [Getting started guide](http://gobblin.readthedocs.org/en/latest/Getting-Started/)
* [Gobblin architecture](http://gobblin.readthedocs.io/en/latest/Gobblin-Architecture/)
+ * Community Slack: [Sign up](https://join.slack.com/t/apache-gobblin/shared_invite/zt-hkwu51id-aVxL3bvtLdi778YHFV1b6A) or [login with existing account](https://apache-gobblin.slack.com) to `apache-gobblin` space on Slack
* [List of companies known to use Gobblin](http://gobblin.readthedocs.io/en/latest/Powered-By/)
* [Sample project](https://github.com/apache/incubator-gobblin/tree/master/gobblin-example)
* [How to build Gobblin from source code](http://gobblin.readthedocs.io/en/latest/user-guide/Building-Gobblin/)
- * [Chat room for users and developers](https://gitter.im/gobblin/Lobby/)
* [Issue tracker - Apache Jira](https://issues.apache.org/jira/projects/GOBBLIN/issues/)
