Fix format of requirements.txt

When trying to `pip install -r requirements.txt`
i got this error:
ValueError: ('Expected version spec in', 'cffi (0.8.6)', 'at', ' (0.8.6)')

…which got solved after changing the format.
I am using pip 1.5.6.
Scrapy does not support Python 3. Change Readme.

Sad, but apparently true :/
https://github.com/scrapy/scrapy/issues/263
Merge pull request #1 from ahx/fix-requirements-txt

Fix format of requirements txt. Use Python 2, because of Scrapy