add omniauth config
generate model for login by using omniauth
insert user model from omniauth
generate controller sessions
add callback after GitHub auth and destroy session to session controller
add routing to create and destroy session
add helper method to judge logged in or not
create login page
change erb to slim
add routing login page
Merge pull request #4 from happy-bonbon0605/fix/erb_to_slim

erbをslimに変換
Merge branch 'master' into create-login-feature
fix typo
first migrate
fix syntax at login button
pluralize Session model
use zocial
fix the place to insert 'require'
remove unused parts from bootstrap
move the description to footer