Updating setup files

setup.py

@@ -84,6 +84,10 @@ def check_dependencies():
         print('Symbolic Python (SymPy) is not installed.\nThis package is required for ' \
               'ParetoLib.\n\nYou can find SymPy at http://www.sympy.org')
         return (False)
+    if (not can_import('cython')):
+        print('Cython is not installed.\nThis package is required for ' \
+              'ParetoLib.\n\nYou can find Cython at https://cython.org/')
+        return (False)
     # Exit automatically if running as part of some script
     # if (not sys.stdout.isatty()):
     #     sys.exit(-1)

setup2.py

@@ -26,7 +26,8 @@ if __name__ == '__main__':
             'numpy>=1.15',
             'pytest>=2.0',
             'sortedcontainers>=1.5.10',
-            'sympy>=1.1.1'
+            'sympy>=1.1.1',
+            'cython>=0.29'
         ],
         #packages_dir={'': 'ParetoLib'},
         #packages=setuptools.find_packages(exclude=['ParetoLib._py3k', 'Tests']),

setup_cython.py

@@ -101,7 +101,8 @@ if __name__ == '__main__':
             'numpy>=1.15',
             'pytest>=2.0',
             'sortedcontainers>=1.5.10',
-            'sympy>=1.1.1'
+            'sympy>=1.1.1',
+            'cython>=0.29'
         ],
         ext_modules=cythonize(module_list=extension_list, exclude=exclude_list, nthreads=cpu_count()),
         # packages_dir={'': 'ParetoLib'},