Release v2.7.0

Release v2.7.0

Fix thread id collision detection not working in Python 2

hashlib returns a byte string in Python 2, but since we only use unicode
strings elsewhere the check against that in
SlackChannelHashedMessages.__missing__ didn't work. Make sure sha1_hex
returns a unicode string instead.

Fixes wee-slack#800, closes wee-slack#801

Release v2.6.0

Release v2.5.0

Release v2.4.0

Release v2.3.0

Release v2.2.0

Release v2.1.1

Release v2.1.0