Fix for UIFlippable when used in combination with other BaseMeshEffects

Unity is very fussy about the order now, so script updated to ensure it's above other base mesh effects on Validate.
(can't solve for stupid if you reorder manually, so updating docs)

Resolves #133

Scripts/Effects/UIFlippable.cs

@@ -5,11 +5,18 @@ namespace UnityEngine.UI.Extensions
 {
     [RequireComponent(typeof(RectTransform), typeof(Graphic)), DisallowMultipleComponent]
     [AddComponentMenu("UI/Effects/Extensions/Flippable")]
-    public class UIFlippable : MonoBehaviour, IMeshModifier
+    public class UIFlippable : BaseMeshEffect
     {     
         [SerializeField] private bool m_Horizontal = false;
         [SerializeField] private bool m_Veritical = false;
-     
+
+#if UNITY_EDITOR
+        protected override void Awake()
+        {
+            OnValidate();
+        }
+#endif
+
         /// <summary>
         /// Gets or sets a value indicating whether this <see cref="UnityEngine.UI.UIFlippable"/> should be flipped horizontally.
         /// </summary>
@@ -29,13 +36,8 @@ namespace UnityEngine.UI.Extensions
             get { return this.m_Veritical; }
             set { this.m_Veritical = value; }
         }
-     
-        protected void OnValidate()
-        {
-            this.GetComponent<Graphic>().SetVerticesDirty();
-        }
-     
-        public void ModifyMesh(VertexHelper verts)
+
+        public override void ModifyMesh(VertexHelper verts)
         {
             RectTransform rt = this.transform as RectTransform;
          
@@ -56,9 +58,21 @@ namespace UnityEngine.UI.Extensions
             }
         }
 
-        public void ModifyMesh(Mesh mesh)
+#if UNITY_EDITOR
+        protected override void OnValidate()
         {
-            //Obsolete member implementation
+            var components = gameObject.GetComponents(typeof(BaseMeshEffect));
+            foreach (var comp in components)
+            {
+                if (comp.GetType() != typeof(UIFlippable))
+                {
+                    UnityEditorInternal.ComponentUtility.MoveComponentUp(this);
+                }
+                else break;
+            }
+            this.GetComponent<Graphic>().SetVerticesDirty();
+            base.OnValidate();
         }
+#endif
     }
 }