don't allow broken distill library versions

`0.9.3` and `0.9.4` versions of the distill library have bug when
dealing with format chains (see raulfraile/distill#13).
bug #87 don't allow broken distill library versions (xabbuh)

This PR was merged into the 1.0-dev branch.

Discussion
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don't allow broken distill library versions

`0.9.3` and `0.9.4` versions of the distill library have bug when
dealing with format chains (see raulfraile/distill#13).

Commits
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1d3b558 don't allow broken distill library versions