Merge pull request #327 from tomaskrizek/cython

setup.py: support compilation with Cython

diff --cc setup.py
index d190eb62f6c6bacc2579af7d70ceaa58f22c609d,5f8427db3f66abdd83c4c6811bf91a8acfd33302..5fb534da4437742d0dec19149c155109fc56f9c1
--- 1/setup.py
--- 2/setup.py
+++ b/setup.py
@@@ -62,8 -71,10 +71,10 @@@ direct manipulation of DNS zones, messa
      'provides': ['dns'],
      'extras_require': {
          'IDNA': ['idna>=2.1'],
 -        'DNSSEC': ['pycrypto>=2.6.1', 'ecdsa>=0.13'],
 +        'DNSSEC': ['pycryptodome', 'ecdsa>=0.13'],
          },
+     'ext_modules': ext_modules if compile_cython else None,
+     'zip_safe': False if compile_cython else None,
      }
  
  setup(**kwargs)