Alter Ruse::Injector#clone to deep copy config

In ruby, Object#clone creates a shallow copy of an object; instance
variables are copied, but not the objects they reference. This means
that when you send #clone to an Injector, previously they would share
the same configuration hash.

This change is intended to support building child injectors, but using
plain ruby semantics (Object#clone).

Example use case in rails:

```ruby
    class User
      attr :repository, :first_name, :last_name

      def initialize(repository, first_name, last_name)
        # set values
      end
    end

    class ApplicationController < ActionController::Base
      before_filter :create_injector

      private

      def create_injector
        @injector = Ruse.create_injector(repository: MyRepository)
      end
    end

    class UsersController < ApplicationController
      def create
        child_injector = @injector.clone
        child_injector.configure(
          values: {
            first_name: params[:first_name],
            last_name:  params[:last_name],
          }
        )
        child_injector.get(:user)
      end
    end
```

In the above example, first_name and last_name may be coming from,
say, a <form> tag, through a params hash.