class Sinatra::Base

def register(*extensions, &block)

extension will be created and registered on the fly.
Register an extension. Alternatively take a block from which an 
def register(*extensions, &block)
  extensions << Module.new(&block) if block_given?
  @extensions += extensions
  extensions.each do |extension|
    extend extension
    extension.registered(self) if extension.respond_to?(:registered)
  end
end