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.