Gemfile in rumble-0.3.7 vs Gemfile in rumble-0.4.0

@@ -1,6 +1,8 @@
-# Copyright (c) 2018 Yegor Bugayenko
+# frozen_string_literal: true
+
+# Copyright (c) 2018-2019 Yegor Bugayenko
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the 'Software'), to deal
 # in the Software without restriction, including without limitation the rights
 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
@@ -17,6 +19,7 @@
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
 source 'https://rubygems.org'
+ruby '~>2.3'
 gemspec