Update pip/setuptools dependencies

Coin still have "special needs" on some systems, but not the same as
pre-weasyprint coin.

That change is after several tests on Jessie and Trusty systems.

README.md

@@ -52,9 +52,10 @@ and `libjpeg-dev` packages.
 
     sudo apt-get install python-dev python-pip libldap2-dev libpq-dev libsasl2-dev libjpeg-dev libxml2-dev libxslt1-dev
 
-You need a setuptools >= 18.5. If you don't meet that requirement (Debian Jessie does not), run:
+You need a recent *pip* for the installation of dependencies to work. If you
+don't meet that requirement (Ubuntu trusty does not), run:
 
-    pip install setuptools>=18.5
+    pip install pip>=1.5.6
 
 In any case, you then need to install coin python dependencies: