zion5un

поправь окончания немного
@contracts = Contract.includes(:departments).order('departments.name asc')

В документации на гитхабе написано:

Friendly reminder
When saving/writing out your rounded images, use an extension that supports transparencies (a.k.a this will not generate rounded jpg images)

Ищем в гугле какие форматы поддерживают и находим ответ:

PNG-24 supports different levels of transparency. Each pixel can have an opacity between 0 and 255 (so 0 is completely transparent).

GIF and PNG-8 both use color palettes, and support transparency only in the form ON or OFF (you select which color should be transparent).

JPG does not support transparency.

devise+pundit тоже неплохо вместе работают

Прочитай про strong_parameters, скринкаст 3 версии

вроде староват, но может пригодится
https://github.com/giano/devise_sms_activable

class ProjectsController < ApplicationController
def create
 		@project = Project.create(name: params[:name])
 		@projects = Project.all
 		authorize(@project)

create.js.coffee
<% if @project.valid? %>

$('.tabs li').removeClass 'last'
$('.tabs').append '<li class=\"last\"><%= j(render @project) %></li>'
notice $('.project-<%= @project.id %>'), '#eaeaae'
$('.tabs input').val ''

<% else %>

notice $('.tabs input'), '#ff6666'
$('.tabs input').val ''
$('.tabs input').attr 'placeholder', '<%= @project.errors[:name].first %>'

<% end %>

index.html.slim

ul.tabs
  li
    = form_tag('/projects', method: :post, remote: true) do
      = text_field_tag(:name, nil, placeholder: 'Новый проект')
  - @projects.each_with_index do |project, index|
    li[class="#{'active' if index == 0}#{' last' if index == @projects.size-1}"]
      = render project