Pin childprocess on older rubies

Author: JonRowe

Gemfile

@@ -21,6 +21,12 @@ else
   gem 'rake', '>= 12.3.3'
 end
 
+if RUBY_VERSION < '2.3.0'
+  gem "childprocess", "< 3.0.0"
+else
+  gem "childprocess", ">= 3.0.0"
+end
+
 ### dep for ci/coverage
 gem 'simplecov', '~> 0.8'