Keep jill as default dependency, only change import strategy

Author: ChrisRackauckas

setup.py

@@ -28,9 +28,6 @@ def readme():
       author_email='[email protected]',
       license='MIT',
       packages=['diffeqpy','diffeqpy.tests'],
-      install_requires=['juliacall>=0.9.14'],
-      extras_require={
-          'julia-install': ['jill']
-      },
+      install_requires=['juliacall>=0.9.14', 'jill'],
       include_package_data=True,
       zip_safe=False)