Upgrade setuptools

I'm hoping this fixes the weird error on Python 3.5 on Appveyor.

Traceback (most recent call last):
  File "c:\python35\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\python35\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "c:\Python35\scripts\zope-testrunner.exe\__main__.py", line 7, in <module>
  File "c:\python35\lib\site-packages\zope\testrunner\__init__.py", line 31, in run
    warnings=warnings)
  File "c:\python35\lib\site-packages\zope\testrunner\__init__.py", line 49, in run_internal
    from zope.testrunner.runner import Runner
  File "c:\python35\lib\site-packages\zope\testrunner\runner.py", line 39, in <module>
    from zope.testrunner.options import get_options
  File "c:\python35\lib\site-packages\zope\testrunner\options.py", line 23, in <module>
    import pkg_resources
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 3017, in <module>
    @_call_aside
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 3003, in _call_aside
    f(*args, **kwargs)
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 3045, in _initialize_master_working_set
    dist.activate(replace=False)
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 2577, in activate
    declare_namespace(pkg)
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 2151, in declare_namespace
    _handle_ns(packageName, path_item)
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 2091, in _handle_ns
    _rebuild_mod_path(path, packageName, module)
  File "c:\python35\lib\site-packages\pkg_resources\__init__.py", line 2120, in _rebuild_mod_path
    orig_path.sort(key=position_in_sys_path)
AttributeError: '_NamespacePath' object has no attribute 'sort'

appveyor.yml

@@ -23,6 +23,7 @@ install:
   - ps: if (-not (Test-Path $env:PYTHON)) { throw "No $env:PYTHON" }
   - 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"
   - python -m pip install -U pip
+  - pip install -U setuptools
   - pip install -U -e .[test]
 
 build: false