[0.3.2] Slack API package upgrade, logging improvements

Just your average periodic maintenance release.

Slack API deprecation changes

• Track inflight messages and retry on error. (#64)
• Bring CI setup into 2021. (#67)
• Use new Slack methods, use go mod, migrate to conversation API (#66)

Stability fixes and Slack changes

• Remove (stale) cached mappings on Slack connect. (#61)
• Move slack API library to github organization repository.
• Improved parsing of rich-text formatted links. (#63)
• Cleanup and update file handling logic to account for new Slack upload flow.

Slack WYSIWYG API fixes

Bump slack client library to handle messages sent from WYSIWYG desktop clients.

Bugfix and Slack changes

• Handle thread broadcasts separately from normal messages, since they no longer trigger normal message events.
• Fix rare panic when parsing malformed Slack messages.
• Update Slack API library version for better disconnect handling.
• More useful logging for multi-workspace instances.

Mark conversations read on message send

Quality of life minor release and bugfix. Fixes a deadlock caused in the Slack RTM client library when the machine loses internet connectivity.

Fix Slack channel join behavior

Previously, channel userlists were empty when a new channel was introduced to a pre-existing IRC connection. This could be fixed by reconnecting to IRC but this fixes the issue entirely.

Bugfixes and Slack changes

• Handle changes Slack made to file uploads in August 2018.
• Block IRC client registration before Slack connection startup to avoid technically correct but undesired operation.
• Fix occasional panic on Ctrl+C.
• Fix occasional panic on startup.

v0.1.2: Use nolanlum/slack fork of nlopes/slack once again.

Changes were made to the way websocket errors are handled to avoid double-disconnects.

Also bump some other deps.

v0.1.1

Ignore slackbot.