added url patterns
added url href 'signup' that goes to 'SignUp'
added sign up form
added a view class about the 'signup'
added template about the 'signup' that shows 'signup page' and a type about the input(POST)
added test code about signup page
modified test code about invalid_password(previous invalid password 'foobar' is 6-digits)
modified the maximum length of the website_url to 255
test code about modified the maximum length of the website_url to 255
added SMTP settings
added a mailing to new user
added a test about the mailing to new user
added requirments (django-smtp-ssl)
remove non-REST features
add user index : show all users
add test : user index page should return 200
add test : user index page should contain users email
add user show : show one user
add test : user show page should contain user info
deleted some useless setting, like djcelery-email (we use django-smtp-ssl)