fixed resolution of parent directory name when calling IndexProcessor

Hi there,

I had a bug when indexing an offline documentation with the following command:
pylookup -u python-2.7.3-docs-html
The indexing processed just fine but the absolute paths in the DB did not contained the directory *python-2.7.3-docs-html*

Here is a fix to get the right parent directory when IndexProcessor is called.

Cheers,
syl20bnr