Add create-react-class dependency

It was added in commit arqex@84755ce but then remove in this commit arqex@752fa8b for no obvious reason. Apparently it's causing some problems for people (arqex#399) so adding it back.

Author: simeg

package.json

@@ -76,6 +76,7 @@
     "webpack-stream": "^3.2.0"
   },
   "dependencies": {
+    "create-react-class": "^15.5.2",
     "@types/react": ">=15",
     "object-assign": "^3.0.0",
     "prop-types": "^15.5.7",