Update Slack invitation link (#8399)

* Update Slack invitation link

* Update remaining Slack links

README.md

@@ -23,7 +23,7 @@ Superset
 [![PyPI version](https://badge.fury.io/py/apache-superset.svg)](https://badge.fury.io/py/apache-superset)
 [![Coverage Status](https://codecov.io/github/apache/incubator-superset/coverage.svg?branch=master)](https://codecov.io/github/apache/incubator-superset)
 [![PyPI](https://img.shields.io/pypi/pyversions/apache-superset.svg?maxAge=2592000)](https://pypi.python.org/pypi/apache-superset)
-[![Get on Slack](https://img.shields.io/badge/slack-join-orange.svg)](https://apache-superset.slack.com)
+[![Get on Slack](https://img.shields.io/badge/slack-join-orange.svg)](https://join.slack.com/t/apache-superset/shared_invite/enQtNDMxMDY5NjM4MDU0LWJmOTcxYjlhZTRhYmEyYTMzOWYxOWEwMjcwZDZiNWRiNDY2NDUwNzcwMDFhNzE1ZmMxZTZlZWY0ZTQ2MzMyNTU)
 [![Documentation](https://img.shields.io/badge/docs-apache.org-blue.svg)](https://superset.incubator.apache.org)
 [![dependencies Status](https://david-dm.org/apache/incubator-superset/status.svg?path=superset/assets)](https://david-dm.org/apache/incubator-superset?path=superset/assets)
 
@@ -130,7 +130,7 @@ Resources
 * [Docker image](https://hub.docker.com/r/amancevice/superset/) (community contributed)
 * [Slides from Strata (March 2016)](https://drive.google.com/open?id=0B5PVE0gzO81oOVJkdF9aNkJMSmM)
 * [Stackoverflow tag](https://stackoverflow.com/questions/tagged/apache-superset)
-* [Join our Slack](https://join.slack.com/t/apache-superset/shared_invite/enQtNDMxMDY5NjM4MDU0LTc2Y2QwYjE4NGYwNzQyZWUwYTExZTdiZDMzMWQwZjc2YmJmM2QyMDkwMGVjZTA4N2I2MzUxZTk2YmE5MWRhZWE)
+* [Join our Slack](https://join.slack.com/t/apache-superset/shared_invite/enQtNDMxMDY5NjM4MDU0LWJmOTcxYjlhZTRhYmEyYTMzOWYxOWEwMjcwZDZiNWRiNDY2NDUwNzcwMDFhNzE1ZmMxZTZlZWY0ZTQ2MzMyNTU)
 * [DEPRECATED Google Group](https://groups.google.com/forum/#!forum/airbnb_superset)
 
 

docs/index.rst

@@ -62,7 +62,7 @@ Superset Resources
   on Github.
 - Our `mailing list archives <https://lists.apache.org/list.html?dev@superset.apache.org>`_.
   To subscribe, send an email to ``dev-subscribe@superset.apache.org``
-- `Join our Slack <https://join.slack.com/t/apache-superset/shared_invite/enQtNDMxMDY5NjM4MDU0LTc2Y2QwYjE4NGYwNzQyZWUwYTExZTdiZDMzMWQwZjc2YmJmM2QyMDkwMGVjZTA4N2I2MzUxZTk2YmE5MWRhZWE>`_
+- `Join our Slack <https://join.slack.com/t/apache-superset/shared_invite/enQtNDMxMDY5NjM4MDU0LWJmOTcxYjlhZTRhYmEyYTMzOWYxOWEwMjcwZDZiNWRiNDY2NDUwNzcwMDFhNzE1ZmMxZTZlZWY0ZTQ2MzMyNTU>`_
 
 Apache Software Foundation Resources
 ====================================