chore(): cleanup return values

Addresses https://github.com/driftyco/ionic-native/issues/38.

src/plugins/launchnavigator.ts

@@ -80,13 +80,10 @@ export class LaunchNavigator {
     successIndex: 2,
     errorIndex: 3
   })
-  static navigate(destination : any, start : any, options? : launchNavigatorOptions) : Promise<any> {
-    // This Promise is replaced by one from the @Cordova decorator that wraps
-    // the plugin's callbacks. We provide a dummy one here so TypeScript
-    // knows that the correct return type is Promise, because there's no way
-    // for it to know the return type from a decorator.
-    // See https://github.com/Microsoft/TypeScript/issues/4881
-    return new Promise<any>((res, rej) => {});
-  }
+  static navigate(
+    destination: any,
+    start: any,
+    options?: launchNavigatorOptions
+  ): Promise<any> { return }
 
 }