Add more tests for ARFF.
Merge branch 'master' of https://github.com/0xdata/h2o-dev
Merge branch 'master' of https://github.com/0xdata/h2o-dev
Merge branch 'master' of https://github.com/0xdata/h2o-dev
Fix TestUtil, was silently swallowing exceptions, and broken tests were passing... bug was introduced in f5155f.