BUG: Fixed regex in asv.conf.json
In https://github.com/pandas-dev/pandas/pull/17293 I messed up the syntax. I
used a glob instead of a regex. According to the docs at
http://asv.readthedocs.io/en/latest/asv.conf.json.html#regressions-thresholds we
want to use a regex. I've actually manually tested this change and verified that
it works.