Use pre node@4 compatible path-exists (#685)

* Revert "Add ES5 version of `path-exists` to CLI"

This reverts commit fc3ab46d2a54f142f9287ce7de9ab2fc2514487d.

* Use pre node@4 compatible `path-exists`

Ref #617

Author: SimenB

package.json

@@ -58,7 +58,7 @@
     "json-loader": "0.5.4",
     "object-assign": "4.1.0",
     "opn": "4.0.2",
-    "path-exists": "3.0.0",
+    "path-exists": "2.1.0",
     "postcss-loader": "0.13.0",
     "promise": "7.1.1",
     "recursive-readdir": "2.0.0",