Replace bundler binstub generated by rails with one from bundler (#46)

Apparently, Rails creates a `bin/bundle` file that ensures all the gems
are installed (yay!) but in doing so, intercepts the flags and arguments
improperly (boo :()

This switches us to use the bundler generated bundler binstub, which
works better, per: rubygems/bundler#6149

.rubocop.yml

@@ -7,7 +7,7 @@ AllCops:
   DisplayStyleGuide: true
   Exclude:
     - db/seeds.rb
-
+    - bin/bundle
 
 Style/StringLiterals:
   EnforcedStyle: double_quotes

bin/bundle

@@ -1,3 +1,103 @@
 #!/usr/bin/env ruby
-ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile", __FILE__)
-load Gem.bin_path("bundler", "bundle")
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'bundle' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "rubygems"
+
+m = Module.new do
+      module_function
+
+  def invoked_as_script?
+    File.expand_path($PROGRAM_NAME) == File.expand_path(__FILE__)
+  end
+
+  def env_var_version
+    ENV["BUNDLER_VERSION"]
+  end
+
+  def cli_arg_version
+    return unless invoked_as_script? # don't want to hijack other binstubs
+    return unless "update".start_with?(ARGV.first || " ") # must be running `bundle update`
+    bundler_version = nil
+    update_index = nil
+    ARGV.each_with_index do |a, i|
+      if update_index && update_index.succ == i && a =~ Gem::Version::ANCHORED_VERSION_PATTERN
+        bundler_version = a
+      end
+      next unless a =~ /\A--bundler(?:[= ](#{Gem::Version::VERSION_PATTERN}))?\z/
+      bundler_version = Regexp.last_match(1) || ">= 0.a"
+      update_index = i
+    end
+    bundler_version
+  end
+
+  def gemfile
+    gemfile = ENV["BUNDLE_GEMFILE"]
+    return gemfile if gemfile && !gemfile.empty?
+
+    File.expand_path("../../Gemfile", __FILE__)
+  end
+
+  def lockfile
+    lockfile =
+      case File.basename(gemfile)
+      when "gems.rb" then gemfile.sub(/\.rb$/, gemfile)
+      else "#{gemfile}.lock"
+      end
+    File.expand_path(lockfile)
+  end
+
+  def lockfile_version
+    return unless File.file?(lockfile)
+    lockfile_contents = File.read(lockfile)
+    return unless lockfile_contents =~ /\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n/
+    Regexp.last_match(1)
+  end
+
+  def bundler_version
+    @bundler_version ||= begin
+      env_var_version || cli_arg_version ||
+        lockfile_version || "#{Gem::Requirement.default}.a"
+    end
+  end
+
+  def load_bundler!
+    ENV["BUNDLE_GEMFILE"] ||= gemfile
+
+    # must dup string for RG < 1.8 compatibility
+    activate_bundler(bundler_version.dup)
+  end
+
+  def activate_bundler(bundler_version)
+    if Gem::Version.correct?(bundler_version) && Gem::Version.new(bundler_version).release < Gem::Version.new("2.0")
+      bundler_version = "< 2"
+    end
+    gem_error = activation_error_handling do
+      gem "bundler", bundler_version
+    end
+    return if gem_error.nil?
+    require_error = activation_error_handling do
+      require "bundler/version"
+    end
+    return if require_error.nil? && Gem::Requirement.new(bundler_version).satisfied_by?(Gem::Version.new(Bundler::VERSION))
+    warn "Activating bundler (#{bundler_version}) failed:\n#{gem_error.message}\n\nTo install the version of bundler this project requires, run `gem install bundler -v '#{bundler_version}'`"
+    exit 42
+  end
+
+  def activation_error_handling
+    yield
+    nil
+  rescue StandardError, LoadError => e
+    e
+  end
+end
+
+m.load_bundler!
+
+load Gem.bin_path("bundler", "bundle") if m.invoked_as_script?