chore(package): update @storybook/addon-knobs to version 4.0.1

Closes #94

Author: greenkeeper[bot]

package.json

@@ -65,7 +65,7 @@
     "@storybook/addon-actions": "^4.0.1",
     "@storybook/addon-events": "^3.3.14",
     "@storybook/addon-info": "^4.0.1",
-    "@storybook/addon-knobs": "^3.3.14",
+    "@storybook/addon-knobs": "^4.0.1",
     "@storybook/addon-links": "^3.3.14",
     "@storybook/addon-options": "^3.3.14",
     "@storybook/addon-storyshots": "^3.3.14",