Migrate CI from Travis CI to GitHub Actions

[mishina2228]

Close #170.

Problem

Since June 15th, 2021, the building on travis-ci.org is ceased.

Solution

This PR migrates CI from Travis CI to GitHub Actions. Here are the details:

• Add Ruby 3.0 and 3.1 to the CI matrix
  • rbx-2 is not included because ruby/setup-ruby does not support it.
• Remove Coveralls
  • Because, according to https://github.com/twitter/twurl/pull/161#issuecomment-765267294, it is not already in use.
• Address changes in RR v3.0.0
  • To use RR v3, we need to take the block as a proc, not as an argument. refs: https://github.com/rr/rr/commit/d6da2090f935cd60cefc7556bcbce9f7964e2be1#diff-a20b4cc1aac26c32a40206ad0776d4ff528201e97b737b7b3f0be1eb0e12e93dL44-L49

• Require OpenStruct v0.3.3+

  • Some test cases failed when running CI in Ruby 3.0.
    Details

    1) Failure:
  Twurl::CLI::OptionParsingTest#test_setting_host_updates_to_requested_value [/home/runner/work/twurl/twurl/test/cli_test.rb:214]:
  Expected: "localhost:3000"
    Actual: "api.twitter.com"
  
    2) Failure:
  Twurl::CLI::OptionParsingTest#test_setting_proxy_updates_to_requested_value [/home/runner/work/twurl/twurl/test/cli_test.rb:237]:
  Expected: "localhost:80"
    Actual: nil
  
    3) Failure:
  Twurl::CLI::OptionParsingTest#test_passing_no_ssl_option_disables_ssl [/home/runner/work/twurl/twurl/test/cli_test.rb:196]:
  Expected false to be truthy.
  
    4) Failure:
  Twurl::CLI::OptionParsingTest#test_specifying_a_request_method_extracts_and_normalizes_request_method [/home/runner/work/twurl/twurl/test/cli_test.rb:54]:
  Expected: "put"
    Actual: "get"
  
    5) Failure:
  Twurl::CLI::OptionParsingTest#test_protocol_is_stripped_from_host [/home/runner/work/twurl/twurl/test/cli_test.rb:221]:
  Expected: "localhost:3000"
    Actual: "api.twitter.com"
  
    6) Failure:
  Twurl::CLI::OptionParsingTest#test_passing_data_and_an_explicit_request_method_uses_the_specified_method [/home/runner/work/twurl/twurl/test/cli_test.rb:148]:
  Expected: "delete"
    Actual: "post"
  
    7) Failure:
  Twurl::Options::Test#test_ssl_is_enabled_if_the_protocol_is_https [/home/runner/work/twurl/twurl/test/cli_options_test.rb:18]:
  Expected false to be truthy.
  
    8) Failure:
  Twurl::Options::Test#test_base_url_is_built_from_protocol_and_host [/home/runner/work/twurl/twurl/test/cli_options_test.rb:13]:
  Expected: "http://api.twitter.com"
    Actual: "https://api.twitter.com"

  • According to https://github.com/twitter/twurl/issues/159#issuecomment-762511975, the cause appears to be a bug in OpenStruct.
  • And the bug was fixed in ruby/ostruct#23, and released as v0.3.3. @smaeda-ks Thanks for letting me know!
• Drop support for Ruby 2.4
  • OpenStruct v0.3.3+ requires Ruby 2.5+.
  • Ruby 2.4 has already reached EOL on 2020-03-31. (Ruby 2.5 and 2.6 has reached EOL also, though)
• Replace the CI status badge on README.md

The CI status can be checked here.

[github-actions[bot]]

CLA Assistant Lite bot All Contributors have signed the CLA. If the commit check is not passing, a maintainer must go the Checks tab of this PR and rerun the GitHub Action.

[CLAassistant]

All committers have signed the CLA.

[mishina2228]

recheck

[mishina2228]

I have read the CLA Document and I hereby sign the CLA

[smaeda-ks]

This looks good to me, thanks @mishina2228