Drop support of eol ruby and rubinius

[unasuke]

Some commits are duplicate to #113 .
Thank you @arunagw 🙏

What is goal of the pull request?

Support to Ruby 2.4.x .

works

• drop support of eol versions
  • CRuby(MRI) 1.8.x and 2.0.x are EOL versions. (ref https://www.ruby-lang.org/en/downloads/)
• use ubuntu trusty to run specs on travis
  • Rubinius 2.x can't install in ubuntu 12.04 using rvm. (ref RVM cannot install rbx-2 on Ubuntu 12.04 Precise rubinius/rubinius#3717)
• drop support of rubinius(add to allow_failures)
  • Specs are passed. But command is can't end(timeout).
  • Current rake is not support to rubinius.
    • ref Drop to rubinius support  ruby/rake#150

[arunagw]

LGTM.. @raysrashmi want to have a look?

[unasuke]

Thanks!