fix(package): update react-codemirror2 to version 7.0.0

Closes #633

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "ramda": "^0.25.0",
     "raven-js": "^3.27.0",
     "react": "^16.5.2",
-    "react-codemirror2": "^5.1.0",
+    "react-codemirror2": "^7.0.0",
     "react-dom": "^16.5.2",
     "react-ga": "^2.5.3",
     "react-loadable": "^5.5.0",