Upgrade calls to insert() and update(), to match with Mongodb driver ~~v2~~ v4's API about openwhyd

[adrienjoly]

merged #64 (automated tests) to master

[adrienjoly]

merged #68 (bug fix #65 : new comment is not displayed properly before page reload)

= good example of fix caused by this mongodb-driver upgrade

[adrienjoly]

doing "insertNotif function in app/models/notifs.js":

• http://localhost:8080/admin/test/notif returns:

clean notifications db => ok
clear all notifications => ok
add sample notifications => ok
clear all notifications => ok
check that db is clean => ok
add sample notifications (again) => ok
clear individual notifications => ok
check that db is clean => ok
call notif.sendTrackToUsers() with no parameters [should fail] => ok
call notif.sendTrackToUsers() without pId parameter [should fail] => ok
call notif.sendTrackToUsers() with a object-typed pId parameter [should fail] => ok
gilles sends a track to me => ok
clear all notifications => ok
gilles sends a playlist to me => NOK
clear all notifications => ok

(1 failing test)

[adrienjoly]

Partially done in #630.

Related to #634.