Merge pull request #24 from pepabo/bump-slack-ruby-client

bundle update slack-ruby-client

Merge pull request #23 from pepabo/fix-warning

fix "method redefined"

Merge pull request #22 from pepabo/fix-broken-tests

Test only the currently maintained Ruby versions

Remove .travis.yml

add ci

Fix circular require

Fix product code assuming tests are correct.

Fixed tests that were not updated to follow changes in the slack-ruby-client.

Merge pull request #21 from pepabo/allow-aliases

refactor(syncable.rb): use YAML.safe_load instead of YAML.load

Merge pull request #20 from pepabo/check-empty-users

Raise when users is empty