implement initial unified/remark preview update

package.json

@@ -157,6 +157,7 @@
     "redux-notifications": "^2.1.1",
     "redux-optimist": "^0.0.2",
     "redux-thunk": "^1.0.3",
+    "rehype-parse": "^3.1.0",
     "rehype-stringify": "^3.0.0",
     "remark-html": "^6.0.0",
     "remark-parse": "^3.0.1",
@@ -168,7 +169,6 @@
     "slug": "^0.9.1",
     "textarea-caret-position": "^0.1.1",
     "unified": "^6.1.4",
-    "unist-util-visit": "^1.1.1",
     "uuid": "^2.0.3",
     "whatwg-fetch": "^1.0.0"
   },