Enable Bundler for Bookshop Projects

[blueheadpublishing]

User should be able to add gem requirements to their bookshop projects by adding them in a Gemfile. This would allow a substantial leveraging of other Ruby gems to build and do cool new functionality within bookshop.

Requires:

• Add Gemfile to config/ folder in bookshop project root
• Add Bundler setup during boot (possibly as part of the script/bookshop file, or nested under a file required by the script/bookshop file:

    # Set up gems listed in the Gemfile.
    ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)

    require 'bundler/setup' if File.exists?(ENV['BUNDLE_GEMFILE'])

• include a Gemfile within templates folder to be built during 'bookshop new project'

source 'https://rubygems.org'

<%= bookshop_gemfile_entry -%>

<%= database_gemfile_entry -%>

<%= assets_gemfile_entry %>
<%= javascript_gemfile_entry %>

# To use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.0.0'

# To use whatever
# gem 'whatever'