def new
      @categories = Category.discussions
      @category = Category.find(params[:cat]) if params[:cat]
      @discussion = Discussion.new
      @discussion.category_id = @category.id if @category
      @discussion.posts.build
      respond_with(@discussion)
    end
def new
      @categories = Category.discussions
      @category = Category.find(params[:cat]) if params[:cat]
      @discussion = Discussion.new
      @discussion.category_id = @category.id if @category
      @discussion.posts.build
      respond_with(@discussion)
    end
GET /cornerstone/discussions/new