create join table for applications and users

has_and_belongs_to_many is the initial association considering the join
table does not need any additional data. If this changes we can change
the association to has_many :through which is much more flexible. For now
we are keeping things fairly simple
use blueprints for test data

gem machinist and faker to mock data
remove unused .keep files for cleanup
include and extend devise helper methods/macros

setup for user_login prior to testing controller methods
WIP landing page upon login

tdd to displays all applications
update README with assignment details