Cleaned up mention regex

src/Discord.Net/Helpers/Mention.cs

@@ -6,8 +6,8 @@ namespace Discord
 {
     public static class Mention
 	{
-		private static readonly Regex _userRegex = new Regex(@"<@(\d+?)>", RegexOptions.Compiled);
-		private static readonly Regex _channelRegex = new Regex(@"<#(\d+?)>", RegexOptions.Compiled);
+		private static readonly Regex _userRegex = new Regex(@"<@(?:\d+?)>", RegexOptions.Compiled);
+		private static readonly Regex _channelRegex = new Regex(@"<#(?:\d+?)>", RegexOptions.Compiled);
 
 		/// <summary> Returns the string used to create a user mention. </summary>
 		public static string User(User user)