[Hanami Issue 921] Support for Ruby version 2.4

[iagus]

Hello!

Just started with Hanami and I thought this issue would be a good opportunity for a first dive-in! And the JRuby version 9.2.0.0 was just released! 💃

I also made this PR for the Devtools repo, so I could check the tests with the rubocop unstable's TargetRubyVersion changed.

To provide as much information as possible:

• To check the tests with the new TargetRubyVersion I modified (not committed) the inherit_form in Devtools' .rubocop-unstable.yml.
• Run the tests! However, got 1 offense:

.....................C..................................................................................................................

Offenses:

lib/hanami/model/migrator/mysql_adapter.rb:26:24: C: Performance/RegexpMatch: Use match? instead of match when MatchData is not used.
          message = if e.message.match(/database exists/) # rubocop:disable Performance/RedundantMatch
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/hanami/model/migrator/mysql_adapter.rb:40:24: C: Performance/RegexpMatch: Use match? instead of match when MatchData is not used.
          message = if e.message.match(/doesn\'t exist/) # rubocop:disable Performance/RedundantMatch
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

• I made the changes requested and re-run the tests:

.....................W..................................................................................................................

Offenses:

lib/hanami/model/migrator/mysql_adapter.rb:26:60: W: Lint/UnneededCopDisableDirective: Unnecessary disabling of Performance/RedundantMatch.
          message = if e.message.match?(/database exists/) # rubocop:disable Performance/RedundantMatch
                                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/hanami/model/migrator/mysql_adapter.rb:40:59: W: Lint/UnneededCopDisableDirective: Unnecessary disabling of Performance/RedundantMatch.
          message = if e.message.match?(/doesn\'t exist/) # rubocop:disable Performance/RedundantMatch
                                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I did as Rubocop commands and removed the directive!

The next tests run looked fine! 🍻 So I understand the last two changes make sense but let me know.

Thank you! 🌷

[jodosha]

@iagus Hi and thanks for this first stab. We can't merge your PRs yet, until Travis won't make JRuby 9.2.0.0 available.

[AlfonsoUceda]

@iagus FYI hanami/devtools#2 has been merged

[jodosha]

@iagus @AlfonsoUceda Please hold on with this. We need first to reach JRuby 9.2 compat for JRuby and then we'll be able to proceed.