added long description

Author: rongxin-liu

setup.py

@@ -15,6 +15,7 @@
         'submit50': [('**.py', 'python', None),],
     },
     description="This is submit50, with which you can submit solutions to problems for CS50.",
+    long_description="This is submit50, with which you can submit solutions to problems for CS50.",
     install_requires=["lib50>=3,<4", "requests>=2.19", "termcolor>=1.1"],
     keywords=["submit", "submit50"],
     name="submit50",