Merge pull request #594 from rubycentral/dependabot/bundler/chartkick-5.1.5

Bump chartkick from 5.1.4 to 5.1.5

Author: amatsuda

Gemfile.lock

@@ -147,7 +147,7 @@ GEM
       xpath (~> 3.2)
     case_transform (0.2)
       activesupport
-    chartkick (5.1.4)
+    chartkick (5.1.5)
     childprocess (5.1.0)
       logger (~> 1.5)
     coderay (1.1.3)