Limit activesupport version

Author: sanemat

Gemfile

@@ -7,6 +7,11 @@ gem 'simplecov'
 
 gem 'yard'
 gem 'markdown'
+if Gem::Version.create(RUBY_VERSION) < Gem::Version.create("2.2.2")
+  # NOTE: markdown depends on textutils, and textutils depends on AS.
+  # AS5 requires Ruby2.2.2 or later.
+  gem 'activesupport', '< 5'
+end
 
 platforms :ruby, :rbx do
   gem 'redcarpet'