8.0 fix pypdf dep

A dependency to pypdf is missing in the file setup.py. It ends with an error when launching odoo :

> Traceback (most recent call last):
>   File "/home/arthur/.virtualenvs/erp8/lib/python2.7/site-packages/werkzeug/serving.py", line 177, in run_wsgi
>     execute(self.server.app)
>   File "/home/arthur/.virtualenvs/erp8/lib/python2.7/site-packages/werkzeug/serving.py", line 165, in execute
>     application_iter = app(environ, start_response)
>   File "/home/arthur/Projets/odoo/openerp/service/server.py", line 280, in app
>     return self.app(e, s)
>   File "/home/arthur/Projets/odoo/openerp/service/wsgi_server.py", line 216, in application
>     return application_unproxied(environ, start_response)
>   File "/home/arthur/Projets/odoo/openerp/service/wsgi_server.py", line 202, in application_unproxied
>     result = handler(environ, start_response)
>   File "/home/arthur/Projets/odoo/openerp/http.py", line 1167, in __call__
>     self.load_addons()
>   File "/home/arthur/Projets/odoo/openerp/http.py", line 1186, in load_addons
>     m = __import__('openerp.addons.' + module)
>   File "/home/arthur/Projets/odoo/openerp/modules/module.py", line 76, in load_module
>     mod = imp.load_module('openerp.addons.' + module_part, f, path, descr)
>   File "/home/arthur/Projets/odoo/addons/report/__init__.py", line 2, in <module>
>     import models
>   File "/home/arthur/Projets/odoo/addons/report/models/__init__.py", line 1, in <module>
>     import report
>   File "/home/arthur/Projets/odoo/addons/report/models/report.py", line 39, in <module>
>     from pyPdf import PdfFileWriter, PdfFileReader
> ImportError: No module named pyPdf

This pull request fixes this.