Bug, tox install command missing from HACKING.
Bug, tox install command missing from HACKING.

Solinea/goldstone-server,slashk/goldstone-server,slashk/goldstone-server,Solinea/goldstone-server,Solinea/goldstone-server,slashk/goldstone-server,slashk/goldstone-server,Solinea/goldstone-server,slashk/goldstone-server,Solinea/goldstone-server