Fix generation of Haml

[willtcarey]

@mwilkins74 had an issue generating his haml files. The Haml gem was asking to install html2haml, but after installing that things were still erroring. Let's figure out what's going on here.

[hannahekehoe]

I didn't have any errors with bundling the haml gem or converting my files, but the code in the book will need updating since generated template views have changed. For example in app/views/books/index.html.haml:

Book version

%p#notice= notice
%h1 Books
%table
  %thead
    %tr
      %th Title
      %th Description
      %th Price
      %th{:colspan => "3"}
  %tbody
    - @books.each do |book|
      %tr
        %td= book.title
        %td= book.description
        %td= book.price
        %td= link_to 'Show', book
        %td= link_to 'Edit', edit_book_path(book)
        %td= link_to 'Destroy', book, method: :delete, data: { confirm: 'Are you sure?' }
%br/
= link_to 'New Book', new_book_path

New code

%p{:style => "color: green"}= notice
%h1 Books
#books
  - @books.each do |book|
    = render book
    %p
      = link_to "Show this book", book
= link_to "New book", new_book_path