[WIP][Polylines] Init polylines directive

Work In Progress to add Polylines to AngularGM:

```html
<gm-map gm-map-id="'myMap'" gm-map-options="mapOptions">
        <gm-polylines gm-objects="polylines"
                      gm-get-coords="object.coords"
                      gm-get-polyline-options="getPolylineOptions(object)">
        </gm-polylines>
</gm-map>
```

```javascript
$scope.mapOptions = {yada: 'yada'};

$scope.getPolyLineOptions = function(line) {
    return {
        strokeColor: '#F00',
        strokeOpacity: 1,
        strokeWeight: 2
    }
}

$scope.polylines = [{coords: [
    {lat: 37.772323, lng: -122.214897}
    {lat: 21.291982, lng:-157.821856},
    {lat: -18.142599, lng: 178.431},
    {lat: -27.46758, lng: 153.027892}
]}];
```

I tried to follow your pattern with how you did the markers. There may be a better way than to have coords as an array of lat/lng objects. Would appreciate some feedback while I continue to work on this (add events, error checking, etc).  Also, I'm going to rename `coords` to `path` to match the Google API.