Remove test files to reduce gem size

[ybiquitous]

Hello. I found that the current published oj gems have included test files, regardless of PR #771.

Do you have any reasons to keep test files in the published gems? Otherwise, do you think it makes sense to remove them?

For your information, I could save about 67KB in my local environment by this gemspec change:

-  s.files = Dir['{lib,ext,test}/**/*.{rb,h,c}'] + ['LICENSE', 'README.md', 'CHANGELOG.md', 'RELEASE_NOTES.md'] + Dir['pages/*.md']
+  s.files = Dir['{lib,ext}/**/*.{rb,h,c}'] + ['LICENSE', 'README.md', 'CHANGELOG.md', 'RELEASE_NOTES.md'] + Dir['pages/*.md']

$ /bin/ls -hl oj-3.16.9.gem*
-rw-r--r--@ 1 masafumi.koba  staff   188K Jan 14 14:43 oj-3.16.9.gem
-rw-r--r--@ 1 masafumi.koba  staff   255K Jan 14 14:30 oj-3.16.9.gem.orig

If you'd like to reject the suggestion, please feel free to close this issue.
Thank you.

[Watson1978]

Thanks. Can you send a Pull Request?