add Rest API unit-tests (db model is mocked); adjust api to match the spec
poc: add users model integration tests: email is unique/required; with test db (requires mongo srv)
add main/signup/login pages; basic navigation logic and stubs for api calls.
adjust grunt build to use new assets
impl passord hashing & store id BD + tests; expose signup/login api and use it on client
impl user session with passport lib: login/logout is handled now
impl menu header switch upon navigation with angular directive