Several devise scopes in one controller


I made a nice feature on top of PR #62
PR adds: 
- possibility to use several devise scopes in one controller simultaneously
- helper methods for manual mode
  - `authenticate_#{entity_underscored}_from_token!` with devise fallback for throwing authentication error  
Example: `authenticate_admin_user_from_token`, `authenticate_user_from_token!`
  - `authenticate_#{entity_underscored}_from_token` without fallback and error  
Example: `authenticate_admin_user_from_token`, `authenticate_admin_user_from_token`

Example of usage:
```ruby
class PostController < ApplicationController
  acts_as_token_authentication_handler_for User, only: [:new, :edit, :create, :update]
  acts_as_token_authentication_handler_for AdminUser, only: [:destroy, :hide, :publish]

  def index
    # ... Accessible for unauthenticated users ...
  end

  def show
    # ... Accessible for unauthenticated users ...
  end

  def new
    # ... Only for authenticated users...
  end

  def edit
    # ... Only for authenticated users...
  end

  def create
    # ... Only for authenticated users...
  end

  def update
    # ... Only for authenticated users...
  end

  def destroy
    # ... Only for authenticated admins...
  end

  def publish
    # ... Only for authenticated admins...
  end

  def hide
    # ... Only for authenticated admins...
  end
end
```