Merge pull request #1 from 39dotyt/developing

Developing
Merge pull request #2 from 39dotyt/developing

fixed update and remove handlers to use ObjectIds instead of strings
Merge pull request #3 from 39dotyt/developing

Implemented attendance request handlers.
Merge pull request #4 from 39dotyt/developing

fixed post-request body hadling
zbs
modified and tested server.js
client updated
Updated client, fixed crash on empty present list on '/attendance/save/'
request.
fixed students update via post requests
updated client
client update
updated client
ObjectId renamed to ObjectID
ObjectId->ObjectID
modified readme and added some comments