setup.py: unpin setuptools_scm (pytest-dev#467)

Fixes pytest-dev#465.

Author: blueyed

setup.py

@@ -28,7 +28,7 @@ def read(fname):
  license='BSD-3-Clause',
  packages=['pytest_django'],
  long_description=read('README.rst'),
- setup_requires=['setuptools_scm==1.11.1'],
+ setup_requires=['setuptools_scm>=1.11.1'],
  install_requires=['pytest>=2.9'],
  classifiers=['Development Status :: 5 - Production/Stable',
  'Framework :: Django',