Added gameserverip field to PlayerSummaryModel/PlayerSummaryResultContainer (#115)

Missing property from https://developer.valvesoftware.com/wiki/Steam_Web_API#GetPlayerSummaries_.28v0002.29

Author: slinkstr

src/Steam.Models/SteamCommunity/PlayerSummaryModel.cs

@@ -100,5 +100,10 @@ public class PlayerSummaryModel
         /// The id of the game that the player is currently playing. This doesn't seem to be an appid, so I'm not sure how to make use of this field.
         /// </summary>
         public string PlayingGameId { get; set; }
+		
+		/// <summary>
+        /// The IP of the server the user is currently playing on.
+        /// </summary>
+        public string PlayingGameServerIP { get; set; }
     }
 }

src/SteamWebAPI2/Models/SteamCommunity/PlayerSummaryResultContainer.cs

@@ -130,6 +130,12 @@ internal class PlayerSummary
         /// </summary>
         [JsonProperty(PropertyName = "gameid")]
         public string PlayingGameId { get; set; }
+		
+		/// <summary>
+        /// The IP of the server the user is currently playing on.
+        /// </summary>
+        [JsonProperty(PropertyName = "gameserverip")]
+        public string PlayingGameServerIP { get; set; }
     }
 
     /// <summary>