Remove unused classnames dependency

Author: lencioni

package.json

@@ -112,7 +112,6 @@
   },
   "dependencies": {
     "airbnb-prop-types": "^2.8.1",
-    "classnames": "^2.2.5",
     "consolidated-events": "^1.1.0",
     "is-touch-device": "^1.0.1",
     "lodash": "^4.1.1",