correct mono runtime detection

src/LogentriesCore/AsyncLogger.cs

@@ -470,14 +470,19 @@ public static bool IsNullOrWhiteSpace(String value)
             return true;
         }
 
+        public static bool isRunningOnMono()
+        {
+            return Type.GetType("Mono.Runtime") != null;
+        }
+
         /* Retrieve configuration settings
          * Will check Enviroment Variable as the last fall back.
          * 
          */
         private string retrieveSetting(String name)
         {
             string cloudconfig = null;
-            if (Environment.OSVersion.Platform == PlatformID.Unix)
+            if (isRunningOnMono())
             {
                 cloudconfig = ConfigurationManager.AppSettings.Get(name);
             }
@@ -604,7 +609,7 @@ protected virtual void WriteDebugMessages(string message)
 
         #endregion
 
-        #region publicMethods
+        #region Public Methods
 
         public virtual void AddLine(string line)
         {