snippet.rb

class PusherWare
  def initialize(app)
    @app = app
    @pusher = Pusher::App.new
  end
  
  def call(env)
    if env["PATH_INFO"] ~= /\/pusher/
      @pusher.call(env)
    else
      @app.call(env)
    end
  end
end

# in Sinatra
use PusherWare