Merge pull request #5 from Zaliro/master

Fix typo in "ApiCredentials", improve "TimestampSecondsConverter" & "WriteCustomBody"

CryptoExchange.Net/Authentication/ApiCredentials.cs

@@ -26,7 +26,7 @@ namespace CryptoExchange.Net.Authentication
         /// <param name="privateKey">The private key used for signing</param>
         public ApiCredentials(SecureString privateKey)
         {
-            PrivateKey = Key;
+            PrivateKey = privateKey;
         }
 
         /// <summary>

CryptoExchange.Net/Converters/TimestampSecondsConverter.cs

@@ -13,7 +13,7 @@ namespace CryptoExchange.Net.Converters
 
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            var t = double.Parse((string)reader.Value, CultureInfo.InvariantCulture);
+            var t = double.Parse(reader.Value.ToString(), CultureInfo.InvariantCulture);
             return new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddSeconds(t);
         }