Remove GetHashCode since Fraction's mutable

Author: napen123

Mathos/Arithmetic/Fraction.cs

@@ -155,16 +155,6 @@ public override bool Equals(object obj)
                 return obj != null && obj.GetType() == GetType() && this == (Fraction) obj;
             }
 
-            /// <summary>
-            /// Returns the hash code for this instance.
-            /// </summary>
-            /// <returns>The hashcode of the fraction.</returns>
-            /// <filterpriority>2</filterpriority>
-            public override int GetHashCode()
-            {
-                return Numerator.GetHashCode() ^ Denominator.GetHashCode();
-            }
-
             /// <summary>
             /// Convert the fraction into a decimal.
             /// </summary>