Swagger ParseModel fixes/improvements

Hi again,

New pull request on top of the master branch.  Wasn't sure if you intended for just the `OrderedDictionary` change, or not?

However, this gives everyone the `DataMember.Order` feature!  I believe my implementation of the ordering to be sound (based on [this MSDN article](http://msdn.microsoft.com/en-us/library/ms729813.aspx)).  Tests are accompanied that match the article.

It'll obviously just skip past if `[DataContract]` is not defined so no additional caveats to consider when including this code?