fixed normalization

Author: petesramek

src/PolylineAlgorithm/PolylineEncoding.cs

@@ -1,4 +1,4 @@
-//
+//
 // Copyright © Pete Sramek. All rights reserved.
 // Licensed under the MIT License. See LICENSE file in the project root for full license information.
 //
@@ -76,10 +76,11 @@ public static int Normalize(double value, uint precision = 5) {
 
         uint factor = Pow10.GetFactor(precision);
 
+        const double Epsilon = 1e-9;
+
         checked {
-            return (int)(Math.Truncate(value * 10 * factor) / 10);
+            return (int)Math.Truncate((value * factor) + (Epsilon * Math.Sign(value)));
         }
-
     }
 
     /// <summary>