We backported MRIv2.0 to use TracePointAPI.
Merge pull request #13 from ygotoh/backport-tpapi-to-MRIv2.0

backporting patch to use TracePointAPI on  MRIv2.0 series.
.travis.yml: remove "rbx-*". add "rbx"

Travis does not support rbx-* anymore.