Bump xhtml2pdf version requirement

Fix broken installation due to https://github.com/xhtml2pdf/xhtml2pdf/issues/318

Still using the chrisglass git version, but I don't know if this is still relevant.

requirements.txt

@@ -11,7 +11,7 @@ django-polymorphic==0.6
 django-sendfile==0.3.6
 django-localflavor==1.1
 -e git+https://code.ffdn.org/zorun/django-postgresql-netfields.git#egg=django-netfields
--e git+https://github.com/chrisglass/xhtml2pdf@a5d37ffd0ccb0603bdf668198de0f21766816104#egg=xhtml2pdf-master
+-e git+https://github.com/chrisglass/xhtml2pdf@386f268c075679c0aa1420dde6b12c5adf45a7e9#egg=xhtml2pdf-master
 -e git+https://github.com/jlaine/django-ldapdb@1c4f9f29e52176f4367a1dffec2ecd2e123e2e7a#egg=django-ldapdb
 feedparser
 six==1.10.0