Add Todo model

* generate and migrate todo model
Add checklist

* configure todo routes
* add TodosController
* add form_for and checklist to admins#index
Show checklist

* add edit button to checklist
* post checklist in users#show
* add js script to checkoff items
* only current_user can see their checklist
Merge pull request #23 from aphuong/checklist

Checklist