Merge pull request #203 from Unity-Technologies/bugfix-preview-node

Make preview node change in width on resizing (fixes #121)

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/MaterialNodeView.cs

             var height = previewNode.height;
 
             m_PreviewTextureView.style.height = height;
+            m_PreviewTextureView.style.width = width;
         }
 
         public void Dispose()