v0.3.0

Added

• Added legacy migration documentation

Changed

• refactored user cache to allow organisation level users/bots #95 (@gdelaney)
• switched files_upload api call (end of life) to files_upload_v2 #109 (@bensodenkamp)

Fixed

• setting SlackRoom purpose. (@jcfrt)
• Fixed channelname raising KeyError: 'is_im'. #103 (@nzlosh)
• Convert bot alternative prefix to slack mention id. #87 (@colincoghill)