Order output not in syn with data-list

[danwos]

If a list of values is given for :data: option of ```.. test-env::``, then the ordering of this list gets lost.
Instead all requested values get printed in alphabetical order.

Example:

.. test-env:: xy.json
   :data: version, name, python

Output order is: name, python, version.

It would be good, if the ordering of :data: can be kept, so that the author can chose how the final result shall look like.

[saifsayyad]

Fixed this bug in #6 pull request