consider returning the target object from set

[focusaurus]

I migrated from a similar module called lodash-deep. It had the nice feature that the set function would return the target object, so you could make a new object from a literal and assign it like this:

var req = pathval.set({}, 'session.token.modelId', new ObjectID());

In pathval, req ends up undefined here.

[keithamus]

@lucasfcosta think we should add this? Seems reasonable.

[lucasfcosta]

@keithamus seems reasonable to me too. Looks like a good idea.
I'll work on it as soon as I get some free time this weekend, it may be a pretty simple thing to do.