[Travis] Test against Ruby `v2.3.1`
[Travis] Test against Ruby `v2.3.1`

asutoshpalai/bundler,RochesterinNYC/bundler,mvz/bundler,bundler/bundler,RochesterinNYC/bundler,asutoshpalai/bundler,dilumnavanjana/bundler,mvz/bundler,dilumnavanjana/bundler,bundler/bundler