module Roda::RodaPlugins::Hooks::ClassMethods

before proc always executes before the previous one.
then instance_execs the existing before proc, so that the given
use a proc that instance_execs the give before proc and
Add a before hook. If there is already a before hook defined,

def before(&block)
  opts[:before_hook] = if b = opts[:before_hook]
    proc do
      instance_exec(&block)
      instance_exec(&b)
    end
  else
    block
  end
end