adds 3.1.1 tag, builds from debian:jessie, removes apt-get upgrade

library/r-base

@@ -1,3 +1,4 @@
 # maintainer: "Carl Boettiger & Dirk Eddelbuettel" [email protected] (@cboettig, @eddelbuettel)
 
 latest: git://github.com/rocker-org/rocker@efc246b8d93905fe3d61e1aea58c8f685c14f3b6 debian/r-base
+3.1.1: git://github.com/rocker-org/rocker@efc246b8d93905fe3d61e1aea58c8f685c14f3b6 debian/r-base