remove redundant cython binding dirctive (#32)

* remove redundant cython binding dirctive

* omit setup.py from coverage

Author: bjlittle

.coveragerc

@@ -8,6 +8,7 @@ include =
     stratify/*
 omit = 
     stratify/tests/*
+    setup.py
 plugins = Cython.Coverage
 
 [report]

setup.py

@@ -52,7 +52,7 @@ def extract_version():
 requirements = ['setuptools>=40.8.0', numpy_req, 'Cython']
 
 extension_kwargs = {}
-cython_directives = {'binding': True}
+cython_directives = {}
 cython_coverage_enabled = os.environ.get('CYTHON_COVERAGE', None)
 if cythonize and cython_coverage_enabled:
     extension_kwargs.update({'define_macros': [('CYTHON_TRACE_NOGIL', '1')]})