Please don't do it.
Latest (tested!) release for 17.x is travelmate 1.0.2. Major LuCI/frontend changes are not in 17.x tree, therefore you will likely receive "unexpected results" ... also please keep in mind that you always update package frontend & backend (check download locations for both package parts here: Travelmate support thread).
In short: if you need latest travelmate package build an image based on 18.06.