beatify code
Merge branch 'master' of https://github.com/tienpx/Nhom12_K57CA
Merge branch 'master' of https://github.com/tienpx/Nhom12_K57CA
use posgresql for production
add gem to enable heroku features
add gem sqlite3
add sqlite3 gem to group development & test
change gem bcrypt -> bcrypt-ruby
change default image for mindmap node
Merge branch 'master' of https://github.com/tienpx/Nhom12_K57CA
add activity diagram