Try to upgrade setuptools

I'm hoping to avoid pypa/setuptools#885 on
Python >= 3.3, e.g. as seen in
https://ci.appveyor.com/project/mgedmin/zope-server/build/1.0.4/job/0udb8qtlnbi5m71e

appveyor.yml

@@ -13,6 +13,7 @@ environment:
 install:
   - "SET PATH=C:\\Python%PYTHON%;c:\\Python%PYTHON%\\scripts;%PATH%"
   - echo "C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\SetEnv.cmd" /x64 > "C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin\amd64\vcvars64.bat"
+  - pip install -U setuptools
   - pip install -e .[test]
 
 build: false