Remove needless files from packed gem

[ybiquitous]

Description

This change aims to reduce the packed gem size by removing needless files.

Also, this removes the test_files option that is not described in the gemspec documentation. See https://guides.rubygems.org/specification-reference/

Changed files

Before: ```console $ gem build && gem unpack pusher-2.0.0.gem $ tree -a pusher-2.0.0 pusher-2.0.0 ├── .github │   ├── stale.yml │   └── workflows │   ├── gh-release.yml │   ├── publish.yml │   ├── release.yml │   └── test.yml ├── .gitignore ├── CHANGELOG.md ├── Gemfile ├── LICENSE ├── README.md ├── Rakefile ├── examples │   ├── async_message.rb │   └── presence_channels │   ├── presence_channels.rb │   └── public │   └── presence_channels.html ├── lib │   ├── pusher │   │   ├── channel.rb │   │   ├── client.rb │   │   ├── request.rb │   │   ├── resource.rb │   │   ├── version.rb │   │   └── webhook.rb │   └── pusher.rb ├── pull_request_template.md ├── pusher.gemspec └── spec ├── channel_spec.rb ├── client_spec.rb ├── spec_helper.rb └── web_hook_spec.rb 8 directories, 27 files ``` After: ```console $ gem build && gem unpack pusher-2.0.0.gem $ tree -a pusher-2.0.0 pusher-2.0.0 ├── .gitignore ├── CHANGELOG.md ├── Gemfile ├── LICENSE ├── README.md ├── Rakefile ├── examples │   ├── async_message.rb │   └── presence_channels │   ├── presence_channels.rb │   └── public │   └── presence_channels.html ├── lib │   ├── pusher │   │   ├── channel.rb │   │   ├── client.rb │   │   ├── request.rb │   │   ├── resource.rb │   │   ├── version.rb │   │   └── webhook.rb │   └── pusher.rb ├── pull_request_template.md └── pusher.gemspec 5 directories, 18 files ```

CHANGELOG

• [CHANGED] Remove needless files from the packed gem.

[elverkilde]

hi @ybiquitous, thank you for this contribution! I opted for a more restrictive approach, only including the lib folder and some docs, see #175. This is now released as 2.0.1.

[ybiquitous]

@elverkilde #175 makes sense! 👍