Defines default setup for authentication.

[#57301716]
Adds slim as a default template engine.

[#57301716]
Removes devise.

Devise is too much of a hassle to configure in order to make it
work for specific requirements.

[#57301716]
Adds bootstrap to application.

[#57301716]
Adds bcrypt to Gemfile

[#57301716]
Defines user model

[#57301716]
Features user sign in and sign up

[#57301716]
Updates home view.

[#57301716]
Removes controller specs for authentication.

[#57301716]
Adds media variables for breakpoints

[#57301716]
Adds integration specs for user sign up and sign in.

[#57301716]
Adds email validations

[#57301716]