Bump rollup from 1.26.2 to 1.27.4 (#393)

Bump rollup from 1.26.2 to 1.27.4

package.json

@@ -75,7 +75,7 @@
     "nodemon": "1.19.4",
     "npm-run-all": "4.1.5",
     "postcss-cli": "6.1.3",
-    "rollup": "1.26.2",
+    "rollup": "1.27.4",
     "rollup-plugin-babel": "4.3.3",
     "rollup-plugin-babel-minify": "9.1.0",
     "rollup-plugin-commonjs": "10.1.0",