public async Task<IEnumerable<TaskModel>> GetTasksAsync()
{
var client = new HttpClient();
client.DefaultRequestHeaders.Add(
"Authorization",
new Signature(this._subscriptionId, this._secretKey).ToString());
var response = await client.GetAsync(_uri);
response.EnsureSuccessStatusCode();
return await response.Content.ReadAsAsync<IEnumerable<TaskModel>>();
}