setup.cfg: Move packages def to options section

Fix packaging with older setuptools.

Author: lwhsu

Diff for: setup.cfg

@@ -8,7 +8,6 @@ license = BSD
 description = Stateful, programmatic web browsing
 long_description = file: README.rst
 url = https://github.com/python-mechanize/mechanize
-packages = mechanize
 classifiers = 
     Development Status :: 5 - Production/Stable
     Intended Audience :: Developers
@@ -37,6 +36,7 @@ classifiers =
     Topic :: Text Processing :: Markup :: XML
 
 [options]
+packages = mechanize
 zip_safe = True
 install_requires = html5lib>=0.999999999