release biocaml 0.3.1
biocaml 0.3.0: make flow dependency required

It was optional, but our way of enabling it optionally is broken. See
biocaml/biocaml#116. For now, making flow required let's users avoid
errors.
biocaml 0.3.0: speed up builds
Merge pull request #1144 from agarwal/biocaml

biocaml updates