Modify DateTime deserialization to return DateTime with DateTimeKind

 Remove what I believe to be a bad DateTime parsing format. It appears redundant to have it when the string literals are almost identical to the DateTime format below it. However, the literal 'Z' causes .NET to not treat the Z as an indication of UTC and instead as a literal which causes the DateTime.Kind to be "unknown".

The result is that when my Json contains "2010-01-01T07:00:00Z" and I explicitly say myDateTime.ToUniversalTime() it adds 8 hours, in my case, to a time that should have already been UTC.