add python-greenlet

from https://code.google.com/p/wallproxy/wiki/OpenWRT
direct link: https://wallproxy.googlecode.com/files/sdk_mf.zip
add gevent

from https://code.google.com/p/wallproxy/wiki/OpenWRT
direct link: https://wallproxy.googlecode.com/files/sdk_mf.zip
gevent: update to 1.0.1, refine Makefile
Merge pull request #3 from zwhfly/python_greenlet_gevent

add greenlet and gevent