fix(package): update styled-components to version 4.1.3

Closes #18

Author: greenkeeper[bot]

package.json

@@ -10,7 +10,7 @@
     "normalize.css": "^7.0.0",
     "react": "^15.5.4",
     "react-dom": "^15.5.4",
-    "styled-components": "^2.0.0"
+    "styled-components": "^4.1.3"
   },
   "devDependencies": {
     "react-scripts": "^1.0.7"