Raised required cython version

Ignore-this: ed6e263f4e3beaecf8f01ca836adb5c2

Cython 0.10.x can't be used anymore since it doesn't seem to support
classes inheriting explicitly from 'object'.

darcs-hash:20100416085307-56b4d-df5586a5c653ae1696c0fd7015e8ebf4ec36e908