Add JSON to the global variables

According to the Wiki only Rhino and Node.js are supported CLI
interfaces, and both have support for a native JSON object. There seems
to be some work to support WSH as well, which has a JSON object as of
version 5.8. WSH 5.8 is used in Windows 7 and onwards, but this may
cause issues still.

Author: Arcanemagus

.jshintrc

@@ -16,6 +16,7 @@
     "undef": true,
     "unused": true,
     "globals": {
-        "CSSLint": true
+        "CSSLint": true,
+        "JSON": true
     }
 }