Adding long description to setup \ pypi (#185)

setup.py

@@ -30,6 +30,8 @@ setup(
     name="hummingbird-ml",
     version=version_str,
     description="Convert trained traditional machine learning models into tensor computations",
+    long_description=long_description,
+    long_description_content_type="text/markdown",
     license="MIT License",
     author="Microsoft Corporation",
     author_email="hummingbird-dev@microsoft.com",