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`.
Not sure why'd you need a separate set of options? If you really need the map to have different options after drawing (instead of resetting the options back to their pre-drawing state), can't you just do something like the following:

```javascript
$scope.map.draw().then(function() {
  $scope.map.options.hello = "world";
  $scope.map.options.blah = "bloo";
});
```