Dispose of log's streamwriter properly.

Fixes issues if TShock is reloaded.

TShockAPI/Log.cs

@@ -131,6 +131,14 @@ namespace TShockAPI
             Write(message, LogLevel.Debug);
         }
 
+        /// <summary>
+        /// Disposes objects that are being used.
+        /// </summary>
+        public static void Dispose()
+        {
+            _logWriter.Dispose();
+        }
+
         /// <summary>
         /// Internal method which writes a message directly to the log file.
         /// </summary>