Rebuild Image using latest Raspbian Stretch

[dcyoung]

Raspbian Stretch Lite is here to replace Raspbian Jessie Lite. For the next release, we should rebuild the image on a fresh copy of Raspbian Stretch Lite.

[dcyoung]

It seems Stretch introduced changes that affect the setup of static IP and WiFi hotspot. Upgrading will have to wait until updated methods are sorted out. Anyone with relevant experience, feel free to chime in.