Update book generation files (#33)

* Update book generation files

I was having trouble generating the book locally, but I made it work
by updating Gemfile and Rakefile files, so they match the versions on
the original book repository.

* Update Rakefile to match publication tool chain

Gemfile

@@ -1,21 +1,16 @@
 source 'https://rubygems.org'
 
 gem 'rake'
-gem 'asciidoctor', '1.5.6.1'
+gem 'asciidoctor', '1.5.6.2'
 
 gem 'json'
 gem 'awesome_print'
 
-gem 'asciidoctor-epub3', :git => 'https://github.com/asciidoctor/asciidoctor-epub3'
-gem 'asciidoctor-pdf', '1.5.0.alpha.16'
-gem 'asciidoctor-pdf-cjk', '~> 0.1.3'
-gem 'asciidoctor-pdf-cjk-kai_gen_gothic', '~> 0.1.1'
+gem 'asciidoctor-epub3', '~> 1.5.0.alpha.9'
+gem 'asciidoctor-pdf', '~> 1.5.0.beta.8'
 
 gem 'coderay'
 gem 'pygments.rb'
 gem 'thread_safe'
-gem 'epubcheck-ruby'
+gem 'epubcheck'
 gem 'kindlegen'
-
-gem 'octokit'
-gem 'github_changelog_generator', github: 'Furtif/github-changelog-generator'

Rakefile

@@ -59,7 +59,7 @@ namespace :book do
     File.open("#{progit_v}.asc", "w") {|file| file.puts new_contents }
 
     puts "Converting to HTML..."
-    exec_or_raise("bundle exec asciidoctor #{progit_v}.asc")
+    exec_or_raise("bundle exec asciidoctor -a data-uri #{progit_v}.asc")
     puts " -- HTML output at #{progit_v}.html"
 
     puts "Converting to EPub..."