Remove non-code files from bundled gem

[greysteil]

First up, thanks for loofah.

The test and benchmark directories for this gem are included in the array of files Rubygems is told are necessary to bundle it, but they can be excluded in order to slim down the gem. It's not a big space saving, as neither are large, but since Loofah is one of the top 100 downloaded gems hopefully it's a saving worth making!

[flavorjones]

Hi @greysteil! Thanks for submitting this PR, and apologies for not responding sooner; somehow this one slipped by me.

I'm in favor of slimming down the final gem by removing unnecessary files, specifically those related to tests. However, this PR edits loofah.gemspec which is a dev-only file that's automatically generated by Hoe. The canonical gem configuration is in the Rakefile as a Hoe configuration.

I'm going to close this PR, but open a new issue asking for the testing files to be removed from the final gem. I recently was involved in similar work for Nokogiri (see sparklemotion/nokogiri#1719) so it's top-of-mind for me.

Thanks again.