SvgUnit comparison seems not to be working so added IsNone() method to...

SvgUnit comparison seems not to be working so added IsNone() method to correctly identify a none type.

Source/DataTypes/SvgUnit.cs

@@ -36,6 +36,14 @@ namespace Svg
             get { return this._isEmpty; }
         }
 
+        /// <summary>
+        /// Gets whether this unit is none.
+        /// </summary>
+        public bool IsNone
+        {
+            get { return _type == SvgUnitType.None; }
+        }
+
         /// <summary>
         /// Gets the value of the unit.
         /// </summary>

Source/DataTypes/SvgUnitCollection.cs

@@ -40,7 +40,7 @@ namespace Svg
                 foreach (string point in points)
                 {
                     SvgUnit newUnit = (SvgUnit)_unitConverter.ConvertFrom(point.Trim());
-                    if(newUnit != SvgUnit.None)
+                    if (!newUnit.IsNone)
                         units.Add(newUnit);
                 }