setup.py: add a long_description

setup.py

@@ -2,9 +2,19 @@
 
 from distutils.core import setup
 
+long_description = '''
+python-libevdev is a Python wrapper arround the libevdev C library. It
+provides a Pythonic API to read events from the Linux kernel's input device
+nodes and to read and/or modify the device's state and capabilities.
+
+The documentation is available here:
+https://python-evdev.readthedocs.io/en/latest/
+'''
+
 setup(name='libevdev',
       version='0.4',
       description='Python wrapper for libevdev',
+      long_description=long_description,
       author='Peter Hutterer',
       author_email='peter.hutterer@who-t.net',
       url='https://www.github.com/whot/python-libevdev/',