Support ruby xyz..end delimiters

[calebmeyer]

In the ruby programming language, blocks are delimited via keywords instead of braces.

class ExampleClass
  def example_method(ruby)
    if ruby
      puts "yep, it's ruby"
    else
      puts "what?"
    end
  end
end

The ends tend to stack up, which is the problem that rainbow-delimiters alleviates for other languages.