Support notifications with Symbol-keyed properties

[ajklein]

Current spec requires "name" to be a String.

[arv]

The only place [*] where this needed an update was in CreateChangeRecord which used to check if name was a string. Now it checks if name is a property key instead.

https://github.com/arv/ecmascript-object-observe/blob/master/NewInternalsSpecification.md#createchangerecordtype-object-name-olddesc-newdesc

[*] I haven't gotten to the array methods yet so leaving this open.

[rektide]

Would love to see progress on this one, it's impacting my codebase. I believe, as per the original filing, symbols should be supported in a manner like strings.

Chrome bug for this: https://code.google.com/p/v8/issues/detail?id=3682