Add retail price to cars table
1. validate retail price.
2. validate uniqueness of submodel by more rules
Refine views
Refine admin's view
1. before_action: find_brand only work in :new, :create, :edit, :update
2. refine validation of car model
Add files into version control
replace tab with spaces for indentation
implement delete car
Rename brand to brand_name (cars table)
Use Guard and LiveReload
add root route
Add brand_name to Car
1. new gem: better_errors
2. new gem: binding_of_caller
3. update gems
add sublime text project file into version control
[stage] temp welcome view
Separate admin layout
uses partials to refine code structure
1. Use car controller instead welcome controller to show car data
[stage] show partial car data
show a random car in index page