fix setup.py install_requires
fix setup.py install_requires

Sadly enough (at least with pip install) package names are case sensitive

setup is trying to install twisted and txamqp instead of Twisted and 
txAMQP
iain-buclaw-sociomantic/carbon,krux/carbon,JeanFred/carbon,mleinart/carbon,pratX/carbon,iain-buclaw-sociomantic/carbon,graphite-project/carbon,johnseekins/carbon,piotr1212/carbon,johnseekins/carbon,pratX/carbon,JeanFred/carbon,pu239ppy/carbon,criteo-forks/carbon,graphite-project/carbon,pu239ppy/carbon,mleinart/carbon,krux/carbon,xadjmerripen/carbon,criteo-forks/carbon,obfuscurity/carbon,kharandziuk/carbon,deniszh/carbon,obfuscurity/carbon,deniszh/carbon,xadjmerripen/carbon,piotr1212/carbon,kharandziuk/carbon