anchor.diff:  To use it we simply treat it like we would any Rack app:
   
   ```ruby
  -run Router.new do
  -  get '/cats', {200, {}, ["Cats!"]}
  -end
  +router = Router.new do
  +  get '/cats' do
  +    [200, {}, ["Cats!"]]
  +  end
  +end
  +
  +run router
   ```
   
   <%= gh_branch 'a-simple-rack-router', 'step-1' %>
  
positive.code: class Router
    attr_accessor :routes
  
    def initialize
      @routes = []
  
      if block_given?
        block = Proc.new
        instance_eval(block)
      end
    end
  
    [:delete, :get, :head, :options, :patch, :post, :put, :trace].each do |verb|
      self.define_method verb do |path, &block|
        routes << Route.new {matcher: path, handler: Proc.new &block }
      end
    end
  
  
negative.code: class Router
    attr_accessor :routes
  
    def initialize(&block)
      @routes = []
      instance_eval(&block) if block_given?
    end
  
    [:delete, :get, :head, :options, :patch, :post, :put, :trace].each do |verb|
  