var user = new CB.CloudUser();
user.set('username', 'my_username');
user.set('password', 'my_password');
user.logIn({
    success: function(response) {
       // do something
    },
    error: function(error) {
       // do something
    }
});

CB.CloudUser {document: Object}
    ACL: (...)
    createdAt: (...)
    document: Object
        ACL: CB.ACL
        _id: "bSzZWFZf"
        _tableName: "User"
        _type: "user"
        _version: 0
        createdAt: "2016-02-12T09:25:32.272Z"
        email: "paco1@mail.com"
        expires: null
        password: "zyF7XhaB685VtWkzv9DdyMJ14f7c7OBCNEXpwHom7rZz62RCbb/WZLAlAiwwHz9iePCzwlXBHmPMT8kyBDO/Bw=="
        updatedAt: "2016-02-12T09:25:32.272Z"
        username: "paco1@mail.com"
        __proto__: Object
    email: (...)
    expires: (...)
    id: (...)
    password: (...)
    updatedAt: (...)
    username: (...)
    __proto__: Object

CB.CloudUser {document: Object}
ACL: (...)
createdAt: (...)
document: Object
    ACL: CB.ACL
    _isModified: true
    _modifiedColumns: Array[4]
    _tableName: "User"
    _type: "user"
    expires: null
    __proto__: Object
email: (...)
expires: (...)
id: (...)
password: (...)
updatedAt: (...)
username: (...)
__proto__: Object