With this command, you'll be able to manage easily the extraction of
URLs from books scanned by KBR

Here is the list of commands and what there are doing:

* make help: display this help
* make pdftotext: this command extract a text version of the PDF files
                  and copy these files to the data/text/ directory
* make extract: running the script to extract URLs found in the text
                files stored in the data/text directory
* make init: if necessary, creates the directories needed