Bump version number for martian release 1.6.0-beta.2
Bump version number for martian release 1.6.0-beta.2

No changes except for the dependency upgrade for mindtouch-http.js -> 1.0.0-beta.2
killsunday/martian,aaronmars/martian,derekrobbins/martian,killsunday/martian,aaronmars/martian,derekrobbins/martian