Bump github.com/nlopes/slack from 0.5.0 to 0.6.0

[dependabot[bot]]

Bumps github.com/nlopes/slack from 0.5.0 to 0.6.0.

Changelog

Sourced from github.com/nlopes/slack's changelog.

v0.6.0 - August 31, 2019

full differences can be viewed using git log --oneline --decorate --color v0.5.0..v0.6.0 thanks to everyone who has contributed since January!

Breaking Changes:

• Info struct has had fields removed related to deprecated functionality by slack.
• minor adjustments to some structs.
• some internal default values have changed, usually to be more inline with slack defaults or to correct inability to set a particular value. (Message Parse for example.)

Highlights:

• new slacktest package easy mocking for slack client. use, enjoy, please submit PRs for improvements and default behaviours! shamelessly taken from the slack-test repo thank you lusis for letting us use it and bring it into the slack repo.
• blocks, blocks, blocks.
• RTM ManagedConnection has undergone a significant cleanup. in particular handles backoffs gracefully, removed many deadlocks, and Disconnect is now much more responsive.

Commits

• 1af34b6 v0.6.0 changelog
• c664c83 support response urls from slash commands
• a6140ff Minor stylistic refactor
• c53487f GetUsersContext bug fixes
• 215bd4e enable setting profiles for other users than the authenticated one
• b7ca1ed Added test with accessory
• ef04826 Fix failing examples
• b66a17c Add URL field to OptionBlockObject
• 2f055ee Only make filename mandatory if Reader is primary method of specifying files
• 9966997 improve disconnect and retry interactions.
• Additional commits viewable in compare view

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