adds static backend returning a list of registered users
enhances call component to handle is online
registers UsersRepository as an injectable
adds isOnline field to fixtures
adds User model
implements a function returning all users
wires up isOnline check
adds global alert component to handle app failures
adds a global-alert to the page
adds a class broadcasting messages
adds global http interceptors
wires everything up in the main file
changes UserRepository to use a more general URL
renames setup in setUp
updates README
Merge branch 'add_backend'