empty rails app
add gem rspec
rails generate rspec:install
add gem capybara
add acceptance spec
add slim gem
set root
add CoinCalculatorController
add coin_calculator views
add gems byebug and better_errors
add visit root
add coin_calculator resource
add create and only trust :amount in parmas
add model coin_calculator
add splitting methods
add coin_input_formatter class
add full coin_input_formatter_spec
wip, add pounds and pence methods
add begin, rescue and valid
refactor, + slightly better error handelling