Remove json support from the generated scaffold

[dira]

The generated coontroller is very verbose, and not so easy on the eyes.

By removing json support we could have code that is simpler, more intuitive, and easier to understand:

# POST /ideas
def create
  @idea = Idea.new(idea_params)

  if @idea.save
    redirect_to @idea, notice: 'Idea was successfully created.'
  else
    render :new
  end
end

# similar for `update` and `delete`

instead of:

# POST /ideas
# POST /ideas.json
def create
  @idea = Idea.new(idea_params)

  respond_to do |format|
    if @idea.save
      format.html { redirect_to @idea, notice: 'Idea was successfully created.' }
      format.json { render :show, status: :created, location: @idea }
    else
      format.html { render :new }
      format.json { render json: @idea.errors, status: :unprocessable_entity }
    end
  end
end

The only downside is that, in order to do that, we need to change
rails new railsgirls

into

rails new railsgirls --skip-bundle
open Gemfile and comment out gem 'jbuilder' bundle install`,

which adds 'weird things' in the beginning. Which is why I'm asking for feedback instead of PR'ing.