Ensure map options are respected after free-drawing polygons

Resolves #952.

It's a bug fix, because there was already code in there to revert the map options after drawing, but it wasn't quite working the right way.

Changes:

* Use `@oldOptions = map.getOptions().options` instead of `@oldOptions = map.getOptions()`.
* Use `@map.setOptions _.defaults @oldOptions, enabledMapOptions` instead of `@map.setOptions _.extend @oldOptions, defaultOptions`.
I am not sure this sure go away. map.getOptions is not officially supported by google maps and this it is a hack thrown into map.coffee. I am considering removing it. Therefore I think it needs to support both for this to work.