Adding new View APIs

v2.2.1 (slackapi#532)

* v2.2.1

Adding new API's & Fixing Bugs

New message builder and bug fixes

Fixing slackapi#422

Bumping version so we can redistribute the package without the deprec…

…ated files. (slackapi#409)

Slack Python SDK v2.0 Official Release

Slack Python SDK v2.0 Beta Release

Version 1.3.1

1.3.0