Use invariant culture when parsing numbers.

src/Markup/Perspex.Markup/Binding/Parsers/LiteralParser.cs

@@ -1,6 +1,7 @@
 // Copyright (c) The Perspex Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
+using System.Globalization;
 using System.Text;
 
 namespace Perspex.Markup.Binding.Parsers
@@ -25,7 +26,7 @@ namespace Perspex.Markup.Binding.Parsers
                     }
                 }
 
-                return int.Parse(result.ToString());
+                return int.Parse(result.ToString(), CultureInfo.InvariantCulture);
             }
 
             return null;

src/Perspex.SceneGraph/Media/Color.cs

@@ -106,7 +106,7 @@ namespace Perspex.Media
                     throw new FormatException($"Invalid color string: '{s}'.");
                 }
 
-                return FromUInt32(uint.Parse(s.Substring(1), NumberStyles.HexNumber) | or);
+                return FromUInt32(uint.Parse(s.Substring(1), NumberStyles.HexNumber, CultureInfo.InvariantCulture) | or);
             }
             else
             {