Safely prepend Publisher initializers

This change alters `Publisher` and `EventExaminer` to use
`Module#prepend` to inject their initializers into the call chain. The
intention is to allow classes that include `Publisher` to include their
own `#initialize` method that still preserves the behavior of
`Publisher#initialize`.

Consider:

    module Foo
      def initialize(*args)
        puts "Foo: #{args.inspect}"
        super
      end
    end

    class A
      include Foo
      def initialize(arg)
        puts "A: #{arg}"
      end
    end

    class B
      prepend Foo
      def initilaize(arg)
        puts "B: #{arg}"
      end
    end

In the case of `A`, since `Foo` is attached via `#include`, the
initializer defined in `Foo` is essentially ignored:

    irb(main):046:0> A.new :foo
    A: :foo
    => #<A:0x007fae191b4a08>

However, in `B`, since `Foo` is attacted via `#prepend`, the initializer
actually ends up behaving as if it were a superclass method of
`B#initialize`:

    irb(main):045:0> B.new :foo
    Foo: [:foo]
    B: :foo
    => #<B:0x007fae191bca28>

This `#prepend` trick works well for your initializers that actually
want to inject behavior during initialization, but ultimately stay out
of the way of any `#initialize` defined by the consuming class.

I ran into this when I tried including `Publisher` in a class that had
an initializer with arguments; I was seeing a "1 for 0" `ArgumentError`.
When I dug into the proofs, I noticed that `ReplayTest` does not
actually have an `#initialize` method of its' own.

My initial effort at producing a failing test was to subclass
`ReplayTest` within the specific proof for testing custom initializers;
however, subclassing overrode the faulty behavior and thus did not
produce a failing test. Instead, I added a constructor argument to
override the `pkey` attribute. It seemed like the least janky way to
introduce a failing test. If I made the proofs worse, I can try and
think of a better way to expose the problem I was trying to solve.

It's worth noting that this change would break ruby 1.9, which does not
have `Module#prepend`.