travis: fix broken ack command
add pypycore.py -> gevent/corecffi.py

from https://github.com/gevent-on-pypy/pypycore/commit/f04a41c0eacfab2662e24291cd63859ecea2f9fe

with code by

Ralf Schmitt
Lucas Clemente Vella
@hasenj
Armin Rigo
corecffi.py: embed ev.c
enable corecffi on pypy
travis: add pypy
corecffi.py: fix pep8
travis/pypy
travis/pypy
corecffi.py: py3 syntax
travis
corecffi.py: fix pyflakes on python34
setup.py: run libev's configure and set zip_safe=False