MapView to support MKPointAnnotation using new attribute annotate in Map...

Summary:
### MapView to support Pin annotation

    var pinLocation = {
			latitude: property.latitude,
			longitude: property.longitude,
			title: property.title
    };
    this.state = {propertyPoint: pinLocation};
    <MapView style={styles.map} region={this.state.region} annotate={this.state.propertyPoint}>
    </MapView>
![mapview-pinannotation](https://cloud.githubusercontent.com/assets/845379/7100280/6c1ffc08-dfe5-11e4-9d1b-8da6a65da1bc.png)

Closes https://github.com/facebook/react-native/pull/810
Github Author: guru inamdar <guru.inamdar@gmail.com>

Test Plan: Imported from GitHub, without a `Test Plan:` line.

Libraries/Components/MapView/MapView.js

@@ -95,6 +95,23 @@ var MapView = React.createClass({
       longitudeDelta: React.PropTypes.number.isRequired,
     }),
 
+    /**
+     * Map annotations with title/subtitle.
+     */
+    annotations: React.PropTypes.arrayOf(React.PropTypes.shape({
+      /**
+       * The location of the annotation.
+       */
+      latitude: React.PropTypes.number.isRequired,
+      longitude: React.PropTypes.number.isRequired,
+
+      /**
+       * Annotation title/subtile.
+       */
+      title: React.PropTypes.string,
+      subtitle: React.PropTypes.string,
+    })),
+
     /**
      * Maximum size of area that can be displayed.
      */
@@ -142,6 +159,7 @@ var MapView = React.createClass({
         pitchEnabled={this.props.pitchEnabled}
         scrollEnabled={this.props.scrollEnabled}
         region={this.props.region}
+        annotations={this.props.annotations}
         maxDelta={this.props.maxDelta}
         minDelta={this.props.minDelta}
         legalLabelInsets={this.props.legalLabelInsets}
@@ -165,6 +183,7 @@ var RCTMap = createReactIOSNativeComponentClass({
       pitchEnabled: true,
       scrollEnabled: true,
       region: {diff: deepDiffer},
+      annotations: {diff: deepDiffer},
       maxDelta: true,
       minDelta: true,
       legalLabelInsets: {diff: insetsDiffer},