chore(tests): use phantomjs on travis, chrome otherwise

there is no need for headless testing when developing,
devs have chrome anyhow. save it for travis.
test(auth): add protractor e2e tests
feat(users): implement user form validation
fix(require): fix path to jquery in requirejs config

closes #144
feat(users): implement checking username existence for new users

close #145
release v0.3