enable directories

Hi.
I have done some work on directories support and also moved code from `src` directory for better development process (it was impossible use `python setup.py develop`) 

To create directory (it should be done manually from mongo client)
`db.insert({'name': test, 'created': '2014-09-12T16:26:51.025Z','lastModified': '2014-09-12T16:26:51.025Z', 'path': ''})`

Now notebooks in root directory should have `"path": ""` and notebooks in 'test' directory should have `"path": "test"`.

Review it please (do not merge yet), I will add the script for importing notebooks bit later.