DOC: rtfd.org -> readthedocs.io

Author: mgeier

setup.py

@@ -79,7 +79,7 @@ def get_tag(self):
     long_description=open('README.rst').read(),
     license='MIT',
     keywords='sound audio PortAudio play record playrec'.split(),
-    url='http://python-sounddevice.rtfd.org/',
+    url='http://python-sounddevice.readthedocs.io/',
     platforms='any',
     classifiers=[
         'License :: OSI Approved :: MIT License',