HACKING: add hacking guidelines with link to C4
Merge pull request #263 from larsbutler/hacking

HACKING: add hacking guidelines with link to C4
Update ns_server.py

netcopy demo can work with multi-nodes
Merge pull request #266 from ArikaChen/master

Update ns_server.py
readme: add build status icon
Merge pull request #270 from mgeisler/readme

readme: add build status icon