travis: add configuration and build script
travis: improve testing
travis: restore lighter benchmarks

Travis kills builds that do not output anything for 10 minutes.
Merge pull request #118 from smondet/test_travis

Integrate travis-ci
travis: send email to biocaml-commits list

Addresses #119.
README: add Travis build status
.gitignore: ignore compiled files in odoc/ dir
Internal_pervasives: remove modules no longer in Core.Std

Core 109.53.00 no longer includes several modules, which we weren’t
using anyway. All were aliases to sexplib modules.
travis: also test with Core 109.53.00
travis: use flow.master