chore(package): update style-loader to version 0.20.0

Closes #64

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
     "leaflet": "1.0.3",
     "leaflet-draw": "^0.4.9",
     "mocha": "^3.2.0",
-    "style-loader": "^0.18.0",
+    "style-loader": "^0.20.0",
     "url-loader": "^0.5.7",
     "webpack": "^3.1.0",
     "webpack-dev-server": "^2.3.0"