Update setup.py for readme.rst

[phalt]

Traceback (most recent call last):
File "", line 17, in
File "/django-twilio/setup.py", line 28, in
'README.md'))).read()
IOError: [Errno 2] No such file or directory:
Complete output from command python setup.py egg_info:
Traceback (most recent call last):

File "", line 17, in

File ""

'README.md'))).read()