Merge pull request #260 from testcontainers/slack-in-docs

add Slack info to the docs

docs/index.md

@@ -28,6 +28,7 @@ This project was initially inspired by a [gist](https://gist.github.com/mosheesh
 ## Contributing
 
 * Star the project on [Github](https://github.com/testcontainers/testcontainers-java) and help spread the word :)
+* Join our Slack: http://slack.testcontainers.org
 * See [ROADMAP](ROADMAP.md) to understand the approach behind the project and what may/may not be in store for the future.
 * [Post an issue](https://github.com/testcontainers/testcontainers-java/issues) if you find any bugs
 * Contribute improvements or fixes using a [Pull Request](https://github.com/testcontainers/testcontainers-java/pulls). If you're going to contribute, thank you! Please just be sure to: