Always use setuptools if availabe

When running `python* setup.py install`, the `jupyter-run` script doesn’t get installed without this.

Author: flying-sheep

setup.py

@@ -70,6 +70,7 @@
     ],
 )
 
+# require setuptools for these cases
 if 'develop' in sys.argv or any(a.startswith('bdist') for a in sys.argv):
     import setuptools
 
@@ -85,7 +86,12 @@
     'test': ['ipykernel', 'ipython', 'mock', 'pytest'],
 }
 
-if 'setuptools' in sys.modules:
+# always try to use setuptools if available
+try:
+    import setuptools
+except ImportError:
+    pass
+else:
     setup_args.update(setuptools_args)
     setup_args['entry_points'] = {
         'console_scripts': [