upgrade bundlesize ^ 0.5.1 (#8)

Author: siddharthkp

package-lock.json

@@ -26,7 +26,7 @@
   "license": "MIT",
   "dependencies": {
     "babel-plugin-transform-decorators-legacy": "1.3.4",
-    "bundlesize": "0.5.0",
+    "bundlesize": "0.5.1",
     "stylis": "0.7.0"
   },
   "devDependencies": {