message: Fix : set language_level. It does not work when using compiler_directives of cythonize.
diff: from setuptools import setup, Extension
  from Cython.Build import cythonize
  from numpy import get_include as numpy_get_include
  +import sys
  __author__ = "Vincent Rouvreau"
  __copyright__ = "Copyright (C) 2016 Inria"
  @@ -38,7 +39,8 @@ for module in modules:
  libraries=libraries,
  library_dirs=library_dirs,
  include_dirs=include_dirs,
  - runtime_library_dirs=runtime_library_dirs,))
  + runtime_library_dirs=runtime_library_dirs,
  + cython_directives = {'language_level': str(sys.version_info[0])},))
  setup(
  name = 'gudhi',
  