PyPI has no requirement that the file is called README or README.txt, so just call it README.rst. In fact, PyPI will not as far as I’m aware look in your package at all (although I could be wrong there, I haven’t studied the code or anything), the text that ends up ion the front is the long_description parameter.
Then in your setup.py, you do something like this:
setup(name="Your module name",
version="1.0",
description="Whatever, dude.",
long_description=open('docs/README.rst', 'rt').read()
)