[android] - added tests for Annotation

platform/android/MapboxGLAndroidSDK/src/main/java/com/mapbox/mapboxsdk/annotations/Annotation.java

@@ -75,19 +75,15 @@ public abstract class Annotation implements Comparable<Annotation> {
         } else if (id > annotation.getId()) {
             return -1;
         }
-
-        // Equal
         return 0;
     }
 
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
-        if (o == null || getClass() != o.getClass()) return false;
-
+        if (o == null || !(o instanceof Annotation)) return false;
         Annotation that = (Annotation) o;
-
-        return getId() == that.getId();
+        return id == that.getId();
     }
 
     @Override