chore(package): update lockfile yarn.lock

Author: greenkeeper[bot]

yarn.lock

@@ -4031,13 +4031,14 @@ rollup-plugin-node-resolve@^3.2.0:
     is-module "^1.0.0"
     resolve "^1.1.6"
 
-rollup-plugin-uglify@^5.0.2:
-  version "5.0.2"
-  resolved "https://registry.yarnpkg.com/rollup-plugin-uglify/-/rollup-plugin-uglify-5.0.2.tgz#3d7985faa9760a933eb451fcfb7f54bf76c0651d"
+rollup-plugin-uglify@^6.0.0:
+  version "6.0.0"
+  resolved "https://registry.yarnpkg.com/rollup-plugin-uglify/-/rollup-plugin-uglify-6.0.0.tgz#15aa8919e5cdc63b7cfc9319c781788b40084ce4"
   dependencies:
     "@babel/code-frame" "^7.0.0"
     jest-worker "^23.2.0"
-    uglify-js "^3.4.8"
+    serialize-javascript "^1.5.0"
+    uglify-js "^3.4.9"
 
 rollup-pluginutils@^2.0.1, rollup-pluginutils@^2.2.0, rollup-pluginutils@^2.3.0:
   version "2.3.1"
@@ -4109,6 +4110,10 @@ sax@^1.2.4:
   version "5.5.1"
   resolved "https://registry.yarnpkg.com/semver/-/semver-5.5.1.tgz#7dfdd8814bdb7cabc7be0fb1d734cfb66c940477"
 
+serialize-javascript@^1.5.0:
+  version "1.5.0"
+  resolved "https://registry.yarnpkg.com/serialize-javascript/-/serialize-javascript-1.5.0.tgz#1aa336162c88a890ddad5384baebc93a655161fe"
+
 set-blocking@^2.0.0, set-blocking@~2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/set-blocking/-/set-blocking-2.0.0.tgz#045f9782d011ae9a6803ddd382b24392b3d890f7"
@@ -4476,7 +4481,7 @@ uglify-js@^2.6:
   optionalDependencies:
     uglify-to-browserify "~1.0.0"
 
-uglify-js@^3.4.8:
+uglify-js@^3.4.9:
   version "3.4.9"
   resolved "https://registry.yarnpkg.com/uglify-js/-/uglify-js-3.4.9.tgz#af02f180c1207d76432e473ed24a28f4a782bae3"
   dependencies: