Add .travis.yaml
.travis.yaml -> .travis.yml
Support rroonga 2.1.2 

https://github.com/ranguba/rroonga/commit/94fd7f0f04828b75755a964cceee16c8b7469e5f
Fix error in 1.8.7
Add test code for TravisCI bug
Add test code for TravisCI bug (#2)
Truncate timestamp.nsec
Add Util#truncate_nsec 
Forget truncate_nsec
Merge branch 'feature/travis-ci' into develop