Revert setup.py changes. Ensure universal wheels.

Attempts at fancy version number handling in setup.py caused more
problems than they were worth, including Travis CI build failures.

The setup.cfg key for universal binary wheel generation apparently
changed at some point, so that was updated as well.

setup.cfg

@@ -1,2 +1,2 @@
-[wheel]
+[bdist_wheel]
 universal = 1

setup.py

@@ -1,6 +1,5 @@
 #!/usr/bin/env python
 from setuptools import setup
-from pelican import __version__
 
 requires = ['feedgenerator >= 1.6', 'jinja2 >= 2.7', 'pygments', 'docutils',
             'pytz >= 0a', 'blinker', 'unidecode', 'six >= 1.4',
@@ -22,7 +21,7 @@ CHANGELOG = open('docs/changelog.rst').read()
 
 setup(
     name="pelican",
-    version=str(__version__),
+    version="3.4.0",
     url='http://getpelican.com/',
     author='Alexis Metaireau',
     author_email='authors@getpelican.com',