chore(package): update extract-text-webpack-plugin to version 3.0.2

Closes #50

Author: greenkeeper[bot]

package.json

@@ -108,7 +108,7 @@
     "eslint-plugin-import": "2.7.0",
     "eslint-plugin-jsx-a11y": "6.0.2",
     "eslint-plugin-react": "7.2.0",
-    "extract-text-webpack-plugin": "3.0.0",
+    "extract-text-webpack-plugin": "3.0.2",
     "file-loader": "0.11.2",
     "glob": "7.1.2",
     "happypack": "4.0.0-beta.3",