step 1. 使用rails script建立project
os:~ $ rails new demo #建立新project,名稱為demo
os:~ $ cd demo
os:~/demo $ rails g controller Say hello #建立controller和view
os:~ $ rails new demo #建立新project,名稱為demo
os:~ $ cd demo
os:~/demo $ rails g controller Say hello #建立controller和view
