Fixed several issues in GrowlService:

1) Calls to the growl SDK were not made in a thread safe manner

2) Loading the icon from a URL did not work in mono, and it made
   the GrowlService calls take exceptionally long

3) The result of the growl SDK calls was not checked

4) A bug in the growl for windows SDK caused the mono version
   on unix platforms to not work. A fixed version of the SDK is
   now included in the build (do not use the NuGet version, it's
   broken on unix). The bug was reported to growl for windows here:
   https://code.google.com/p/growl-for-windows/issues/detail?id=48
Wall of code. This is more readable.

```
_logger.Debug("Sending Notification to: {0}:{1}", hostname, port);

var growlConnector = new GrowlConnector(password, hostname, port);
var result = new GrowlResult();
var notificationType = _notificationTypes.Single(n => n.Name == notificationTypeName);
var notification = new GrowlNotification(_growlApplication.Name, notificationType.Name, DateTime.Now.Ticks.ToString(), title, message);
            
growlConnector.OKResponse += GrowlOKResponse;
growlConnector.ErrorResponse += GrowlErrorResponse;

growlConnector.Notify(notification, result);
result.Wait(10000);
```