Fix: No cmd option specified, unable to run specs!
Setup travis-ci
[ci skip] tweak doc
[ci skip] Add badge
Merge pull request #10 from sue445/feature/cmd_option

guardが動いていなかったのを修正
Merge pull request #11 from tddbc/feature/setup_travis_ci

Travis CI連携
Add power_assert example
power_assert is support only ruby 2.x