#4 Move Find into Model

Move a find into the model to clean up the controllers and remove duplication. Also see how you can call these custom find methods through an association.

# tasks_controller.rb
def index
  @tasks = Task.find_incomplete
end

# models/task.rb
def self.find_incomplete
  find_all_by_complete(false, :order => 'created_at DESC')
end

# projects_controller.rb
def show
  @project = Project.find(params[:id])
  @tasks = @project.tasks.find_incomplete
end