Reduce gem size by excluding test files

[yuri-zubov]

This pull request updates the *.gemspec file to optimize the gem package size and structure

$ gem build -o before.tar

$ git switch reduce-gem-size

$ gem build -o after.tar

$ du -sh before.tar after.tar
 16K	before.tar
 12K	after.tar

Metric	Before	After	Saved
Size	16K	12K	−4K

whitch files was deleted?

data
 ├── lib
 │   ├── simplecov-console
 │   │   └── output
 │   │       ├── block.rb
 │   │       └── table.rb
 │   └── simplecov-console.rb
-├── test
-│   ├── helper.rb
-│   └── test_simplecov-console.rb
-├── .document
 ├── CHANGELOG.md
-├── Gemfile
 ├── LICENSE.txt
-├── Rakefile
 ├── README.md
-├── simplecov-console.gemspec
-└── VERSION

ps: you can see on rails repo

[chetan]

@yuri-zubov appreciate the PR! We're using juwelier to generate the gem (for better or worse). Do you mind modifying your PR to set the list of files like this?

[yuri-zubov]

@yuri-zubov appreciate the PR! We're using juwelier to generate the gem (for better or worse). Do you mind modifying your PR to set the list of files like this?

@chetan done