Feature/login

[jinyung2]

• implemented login page using template of signup
• refactored into a signuplogin container
• separate signup and login components
• functions to handle onchange and submit of form
• implemented bootstrap alert for error message

@tessa-tapmongkol I dont know how you like to handle components that are direct children to a particular component, but atm I just left it in the same folder as the SignUpLogIn (I refactored this, it was previously named SignUpPage I think). If there is something you want changed here please leave a comment on PR.