Remove development and test files from the gem package

[orien]

There are a number of files in the gem package that aren't useful for downstream projects. Removing these reduces the gem package size from 118K to 7K!

< .gitignore
< .travis.yml
  CHANGELOG.md
< Gemfile
  LICENSE
  README.md
< Rakefile
  ext/mkrf_conf.rb
  lib/unf.rb
  lib/unf/normalizer.rb
  lib/unf/normalizer_cruby.rb
  lib/unf/normalizer_jruby.rb
  lib/unf/version.rb
< test/helper.rb
< test/normalization-test.txt
< test/test_unf.rb
< unf.gemspec

[t-richards]

Seems like this project might not accept changes of this kind. See #17 for a previous attempt which lingered for nearly two years without response.

[orien]

🍃