Fixes #497 (#498)
Fixes #497 (#498)

* Fixes #497

  - Removes slack invite link

* Fixes #497

  - Updates slack url to https://join.slack.com/t/kubeflow/shared_invite/enQtNDg5MTM4NTQyNjczLWUyZGI1ZmExZWExYWY4YzlkOWI4NjljNjJhZjhjMjEwNGFjNmVkNjg2NTg4M2I0ZTM5NDExZWI5YTIyMzVmNzM
  - This link allows a member of the general public (who doesn't have
  either a google, microsoft, or caicloud address) to
  sign up for the slack channel with an auto-generated invite

kubeflow/examples,kubeflow/examples,kubeflow/examples,kubeflow/examples