Bump clockwork from 2.0.3 to 2.0.4

Bumps [clockwork](https://github.com/Rykian/clockwork) from 2.0.3 to 2.0.4.
- [Release notes](https://github.com/Rykian/clockwork/releases)
- [Changelog](https://github.com/Rykian/clockwork/blob/master/CHANGELOG.md)
- [Commits](Rykian/clockwork@v2.0.3...v2.0.4)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -111,7 +111,8 @@ GEM
     cf-uaa-lib (3.14.3)
       httpclient (~> 2.8, >= 2.8.2.4)
       multi_json (~> 1.12.0, >= 1.12.1)
-    clockwork (2.0.3)
+    clockwork (2.0.4)
+      activesupport
       tzinfo
     cloudfront-signer (3.0.2)
     codeclimate-test-reporter (1.0.9)