Added support for specifying additional marker options

I added some code to *src/services/leafletMarkerHelpers.js* to support additional marker options. I needed this code to support [leaflet.bouncemarkers](https://github.com/maximeh/leaflet.bouncemarker). Now, the following code to my controller class makes my markers fall from the top on creation.

```javascript
$scope.markers[ent._id] = {
    lat: ent.latlng.lat
  , lng: ent.latlng.lng 
  , icon: icon
  , draggable: false
  , message: 'Hello, I am a marker'
  , bounceOnAdd: true
};
```