Ruby support

[noraj]

In his paper, Alex BIRSAN talked about dependency confusion in Ruby (index: Rubygems, package manager: gem) with an example with shopify-cloud gem.
Would it be possible to support gems too (Gemfile, Gemfile.lock, *.gemspec)?

[DreyAnd]

^^ would be a really useful addition.

[rzhade3]

This has been added as of #40. Can we close out this issue?

[noraj]

1. I have created Readme: add rubygems in description #42 to reflect it in the README
2. ruby and rubygems could be added in the repo tags too:

3. Ruby is already mentioned in the Usage and Example section of the README.