I set up my wifi this way by directly editing the sd card, but I was unaware that SSH could be enabled this way.
I am using Raspbian Jessie Lite, released in March 2017. They now have SSH disabled by default which is annoying.
Ultimately it would be best if there was a utility for setting up a SD card properly (set up Wi-Fi, install particle-agent, change hostname, change password, enable SSH, etc). I think @jvanier was thinking about this, incorporating it into particle-cli perhaps.