Make installable from sdist without cython

MANIFEST.in

@@ -0,0 +1 @@
+recursive-include greedy *.h *.cpp *.pxd *.pyx

greedy/composite.py

@@ -47,7 +47,7 @@ def __init__(self, child_sampler):
         self.children = [child_sampler]
 
         # set the parameters
-        self.parameters = parameters = child_sampler.parameters.copy()
+        self.parameters = child_sampler.parameters.copy()
 
         # set the properties
         self.properties = dict(child_properties=child_sampler.properties.copy())

greedy/descent.pyx

@@ -1,6 +1,7 @@
 # distutils: language = c++
 # distutils: include_dirs = greedy/src/
 # distutils: sources = greedy/src/descent.cpp
+# distutils: language_level = 3
 
 # Copyright 2019 D-Wave Systems Inc.
 #

setup.py

@@ -90,6 +90,7 @@ def finalize_options(self):
 extensions = [Extension(
     name='greedy.descent',
     sources=['./greedy/descent.pyx'],
+    include_dirs=['./greedy/src/']
 )]
 
 classifiers = [