Added active-support dependency.

Author: dblock

CHANGELOG.md

@@ -1,5 +1,6 @@
 ### 0.16.1 (Next)
 
+* [#271](https://github.com/slack-ruby/slack-ruby-bot/pull/271): Added explicit dependency on `activesupport` - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 ### 0.16.0 (2020/7/26)

slack-ruby-bot.gemspec

@@ -17,6 +17,7 @@ Gem::Specification.new do |s|
   s.licenses = ['MIT']
   s.summary = 'The easiest way to write a Slack bot in Ruby.'
   s.required_ruby_version = '>= 2.3'
+  s.add_dependency 'activesupport'
   s.add_dependency 'hashie'
   s.add_dependency 'slack-ruby-client', '>= 0.14.0'
   s.add_development_dependency 'rack-test'