Refactored to eliminate static ServiceModelConfig due to failing afte…

[bvandehey]

The UrbanAirSharp library fails after 160 requests if your program creates a new instance of the UrbanAirshipGateway for each request. Due to our multi-tenant application, this is a requirement. The reason it fails is due to the static ServiceModelConfig class which contains a static reference to the HttpClient class. I have refactored the code to change ServiceModelConfig from a static class to an instance class which eliminates this issue.

[bvandehey]

Here's a simple program that replicates the failure at 160 requests:

class Program
{
    private static int count = 0;
    static void Main(string[] args)
    {
        for (int i = 0; i < 200; i++)
        {
            SendUASMessage();
        }

    }

    public static void SendUASMessage()
    {
        var client = new UrbanAirSharpGateway("{appkey}", "{secretkey");
        Audience audience = new Audience(AudienceType.Android, "{devicekey}");
        string message = "(Test Message)";
        var response = client.Push(message, null, null, null, audience);
        count++;
        Console.WriteLine(!response.Ok
                              ? $"{count} - Urban Airship Error: {response.Message}"
                              : $"{count} - {response.Message}");
    }
}