seperated todoist and habitica api calls into services

Habitica.Todoist.Integration.Model/Todoist/Due.cs

@@ -1,4 +1,5 @@
-using System;
+using Newtonsoft.Json;
+using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Text;
@@ -7,8 +8,11 @@ namespace Habitica.Todoist.Integration.Model.Todoist
 {
     public class Due
     {
+        [JsonProperty("date")]
         public string Date { get; set; }
+        [JsonProperty("timezone")]
         public string Timezone { get; set; }
+        [JsonProperty("string")]
         public string @String { get; set; }
 
         public string ToJavaScriptDateStr()