Update dependencies

Force ruby >=2.0.0 to do like ohai
Remove Strainerfile and replace it with Rakefile
Remove version in cookbook Gemfile and remove deprecated warnings
Remove version in Gemfile
Remove 1.9.3 and add 2.1.0 ruby versions
Remove strainer in gemspec file and .travis.yml file
Merge pull request #1 from Numergy/update-dependencies

Update dependencies