Fix a jshint warning

Because __proto__ has been revived in ES6, I've kept it.

Five warnings
31	The '__proto__' property is deprecated.
32	The '__proto__' property is deprecated.
33	The '__proto__' property is deprecated.
45	The '__proto__' property is deprecated.
54	The body of a for in should be wrapped in an if statement to filter unwanted properties from the prototype.