Changed type of ReleaseDate (DateTime --> String). JSON.NET wasn't able to parse some timestamps

Author: Johnny @PC

SpotifyAPI/SpotifyWebAPI/Models/FullAlbum.cs

@@ -34,7 +34,7 @@ public class FullAlbum : BasicModel
         [JsonProperty("popularity")]
         public int Popularity { get; set; }
         [JsonProperty("release_date")]
-        public DateTime ReleaseDate { get; set; }
+        public String ReleaseDate { get; set; }
         [JsonProperty("release_date_precision")]
         public String ReleaseDatePrecision { get; set; }
         [JsonProperty("tracks")]