Fixed Rectangle snapping.

Perspex.Controls/Border.cs

@@ -51,7 +51,7 @@ namespace Perspex.Controls
             Brush background = this.Background;
             Brush borderBrush = this.BorderBrush;
             double borderThickness = this.BorderThickness;
-            Rect rect = new Rect(this.Bounds.Size).Deflate(this.BorderThickness / 2);
+            Rect rect = new Rect(this.Bounds.Size).Deflate(this.BorderThickness);
 
             if (background != null)
             {

Perspex.Controls/Shapes/Ellipse.cs

@@ -20,8 +20,7 @@ namespace Perspex.Controls.Shapes
             {
                 if (this.geometry == null || this.geometrySize != this.Bounds.Size)
                 {
-                    var rect = new Rect(0, 0, this.Bounds.Size.Width, this.Bounds.Size.Height);
-                    rect = rect.Deflate(this.StrokeThickness / 2);
+                    var rect = new Rect(this.Bounds.Size).Deflate(this.StrokeThickness);
                     this.geometry = new EllipseGeometry(rect);
                     this.geometrySize = this.Bounds.Size;
                 }

Perspex.Controls/Shapes/Rectangle.cs

@@ -20,7 +20,8 @@ namespace Perspex.Controls.Shapes
             {
                 if (this.geometry == null || this.geometrySize != this.Bounds.Size)
                 {
-                    this.geometry = new RectangleGeometry(new Rect(0, 0, this.Bounds.Size.Width, this.Bounds.Size.Height));
+                    var rect = new Rect(this.Bounds.Size).Deflate(this.StrokeThickness);
+                    this.geometry = new RectangleGeometry(rect);
                     this.geometrySize = this.Bounds.Size;
                 }
 

Perspex.SceneGraph/Rect.cs

@@ -302,7 +302,7 @@ namespace Perspex
         /// <remarks>The deflated rectangle size cannot be less than 0.</remarks>
         public Rect Deflate(double thickness)
         {
-            return this.Deflate(new Thickness(thickness));
+            return this.Deflate(new Thickness(thickness / 2));
         }
 
         /// <summary>