Dev/folders as tags

Hi,

I've made a change to flickrannex to allow having directories as tags to uploads.

Directories below the top level git directory are added as tags to uploads:
    ```/home/me/annex-photos/holidays/2013/Greenland/img001.jpg```
would get the following tags:  ```holidays``` ```2013``` ```Greenland```
(where "/home/me/annex-photos" is the top level in the annex)

Hope you are happy to merge this change.


Olaf