added a rest api tool

Added a simple rest api tool, 
can be used like this:
```
from vsc.utils.rest import RestClient
r = RestClient('https://account.vscentrum.be/django/api', token='some oauth token', bearer='Bearer')
print r.account['vsc40xxx'].person.get()[1]['gecos']
```
The point is to very easily set up a call to a rest api, and possibly subclass this for your own REST api you want to use, so can instantiate it with only a token.