feat(SebmGoogleMap): support map click event

Now, you can subscribe to map click events:

```
<sebm-google-map
  [latitude]="lat"
  [longitude]="lng"
  (mapClick)="mapClicked($event)">
</sebm-google-map>
```

The $event is a `MapMouseEvent` type that contains
the coords of the click.

```
import {MapMouseEvent} from 'angular2-google-maps/core';

mapClicked(event: MapMouseEvent) {
  console.log(event.coords.lat, event.coords.lng);
}
```

docs/api/components_directives/sebmGoogleMap.md

@@ -18,7 +18,7 @@ import {SebmGoogleMap} from 'angular2-google-maps/core';
 ```
 
 ```html
-<sebm-google-map [latitude]="lat" [longitude]="lng" [zoom]="zoom">
+<sebm-google-map [latitude]="lat" [longitude]="lng" [zoom]="zoom" (mapClick)="mapClicked($event)">
 </sebm-google-map>
 ```
 
@@ -32,4 +32,15 @@ import {SebmGoogleMap} from 'angular2-google-maps/core';
 
 ### Events
 
-None
+| Event name | Arguments                       | Description                                  |
+|------------|---------------------------------|----------------------------------------------|
+| mapClick   | [MapMouseEvent](#MapMouseEvent) | Gets emitted when the user clicks on the map |
+
+### Event Interfaces
+
+#### MapMouseEvent <a name="mapClickEvent"></a>
+```typescript
+interface MapMouseEvent {
+  coords: LatLngLiteral // { lat: number, lng: number }
+}; 
+```

src/directives.ts

@@ -1,3 +1,3 @@
-export {SebmGoogleMap} from './directives/google-map';
+export {SebmGoogleMap, MapMouseEvent} from './directives/google-map';
 export {SebmGoogleMapMarker} from './directives/google-map-marker';
 export {ANGULAR2_GOOGLE_MAPS_DIRECTIVES} from './directives-const';

src/directives/google-map.ts

@@ -1,7 +1,7 @@
-import {Component, Input, Renderer, ElementRef} from 'angular2/core';
+import {Component, Input, Output, Renderer, ElementRef, EventEmitter} from 'angular2/core';
 import {GoogleMapsAPIWrapper} from '../services/google-maps-api-wrapper';
 import {MarkerManager} from '../services/marker-manager';
-import {LatLng} from '../services/google-maps-types';
+import {LatLng, LatLngLiteral} from '../services/google-maps-types';
 
 /**
  * Todo: add docs
@@ -28,6 +28,8 @@ export class SebmGoogleMap {
   private _zoom: number = 8;
   private _mapsWrapper: GoogleMapsAPIWrapper;
 
+  @Output() mapClick: EventEmitter<MapMouseEvent> = new EventEmitter<MapMouseEvent>();
+
   constructor(elem: ElementRef, _mapsWrapper: GoogleMapsAPIWrapper, renderer: Renderer) {
     this._mapsWrapper = _mapsWrapper;
     renderer.setElementClass(elem, 'sebm-google-map-container', true);
@@ -39,6 +41,7 @@ export class SebmGoogleMap {
     this._mapsWrapper.createMap(el, this._latitude, this._longitude);
     this._handleMapCenterChange();
     this._handleMapZoomChange();
+    this._handleMapClick();
   }
 
   @Input()
@@ -93,4 +96,17 @@ export class SebmGoogleMap {
     this._mapsWrapper.subscribeToMapEvent<void>('zoom_changed')
         .subscribe(() => { this._mapsWrapper.getZoom().then((z: number) => this._zoom = z); });
   }
+
+  private _handleMapClick() {
+    this._mapsWrapper.subscribeToMapEvent<{latLng: LatLng}>('click')
+        .subscribe((event: {latLng: LatLng}) => {
+          this.mapClick.emit(
+              <MapMouseEvent>{coords: {lat: event.latLng.lat(), lng: event.latLng.lng()}});
+        });
+  }
 }
+
+/**
+ * MapMouseEvent gets emitted when the user triggers mouse events on the map.
+ */
+export interface MapMouseEvent { coords: LatLngLiteral; }