ES6 compliant Object.keys
Use ES6 `keys` where applicable
Spec compliant `Object.assign`
Add `assign` like error handling to `Object.clear`
Compliant error handling
Add (as introduced with ES6) Array#copyWithin
Add (as introduced with ES6) Array#fill
Improve Array.prototype.filter handling
Fallback to native Array#find
Fallback to native Array#findIndex
Improve Array.prototype.map handling
Improve Array.prototype.slice handling
Improve Array.prototype.splice handling