add ignore_field_order parameter to Vlad class

[gregorkschroeder]

Issue #43

[di]

Thanks @gregorkschroeder!

The main issue I have with this is that validators is a dictionary, and in Python dictionaries do not have guaranteed order (although sometimes it seems like we can get away with it).

For example, your test might actually fail on some systems and in some versions of Python.

For this to be mergeable, we'd either have to check if the user has made validators an OrderedDict, or allow the user to supply an argument such as column_order. I somewhat prefer the latter, because the presence of this optional arg would also obviate the need for the ignore_field_order argument.

[gregorkschroeder]

I agree the second option is much preferable. Will re-submit a pull request.