Add clear timeout polyfill

CHANGELOG.md

@@ -5,6 +5,10 @@ Contributors: please follow the recommendations outlined at [keepachangelog.com]
 
 ## [Unreleased]
 
+## [6.0.4]
+##### Fixed
+- Added polyfill for clearTimeout which is used by babel-polyfill.
+
 ## [6.0.3]
 ##### Fixed
 - Added assets symlinking support on Heroku [#446](https://github.com/shakacode/react_on_rails/pull/446) by [Alexey Karasev](https://github.com/alleycat-at-git).
@@ -345,7 +349,8 @@ Best done with Object destructing:
 ##### Fixed
 - Fix several generator related issues.
 
-[Unreleased]: https://github.com/shakacode/react_on_rails/compare/6.0.3...master
+[Unreleased]: https://github.com/shakacode/react_on_rails/compare/6.0.4...master
+[6.0.4]: https://github.com/shakacode/react_on_rails/compare/6.0.3...6.0.4
 [6.0.3]: https://github.com/shakacode/react_on_rails/compare/6.0.2...6.0.3
 [6.0.2]: https://github.com/shakacode/react_on_rails/compare/6.0.1...6.0.2
 [6.0.1]: https://github.com/shakacode/react_on_rails/compare/6.0.0...6.0.1

lib/react_on_rails/server_rendering_pool/exec.rb

@@ -132,6 +132,10 @@ def execjs_timer_polyfills
 function setTimeout() {
   #{undefined_for_exec_js_logging('setTimeout')}
 }
+
+function clearTimeout() {
+  #{undefined_for_exec_js_logging('clearTimeout')}
+}
           JS
         end