Chassis failing experiment

app.rb

require 'rubygems'
require 'bundler/setup'
require 'chassis'

class Post
  attr_accessor :id, :title, :text
end

repo = Chassis::Repo.default

puts repo.empty? Post #=> true

post = Post.new
post.title = 'Such Repos'
post.text = 'Very wow. Much design.'

repo.save post

puts post.id #=> 1

Error

/Projects/my/repositories-experiment > ruby app.rb
/Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis/strategy.rb:83:in `included': private method `include' called for Chassis::Repo:Class (NoMethodError)
	from /Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis/repo.rb:19:in `include'
	from /Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis/repo.rb:19:in `<class:Repo>'
	from /Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis/repo.rb:18:in `<module:Chassis>'
	from /Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis/repo.rb:1:in `<top (required)>'
	from /Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis.rb:63:in `require_relative'
	from /Users/inem/.rvm/gems/ruby-2.0.0-p353@my/bundler/gems/chassis-2504d3d17788/lib/chassis.rb:63:in `<top (required)>'
	from app.rb:3:in `require'
	from app.rb:3:in `<main>'

Gemfile

source 'https://rubygems.org'

gem 'chassis', git: 'https://github.com/ahawkins/chassis.git'