chore(Dockerfile): update go toolchain to 1.7.1

See https://github.com/golang/go/issues?q=milestone%3AGo1.7.1

Author: mboersma

rootfs/Dockerfile

@@ -1,6 +1,6 @@
 FROM quay.io/deis/base:0.3.1
 
-ENV GO_VERSION=1.7 \
+ENV GO_VERSION=1.7.1 \
     GLIDE_VERSION=v0.12.1 \
     GLIDE_HOME=/root \
     PATH=$PATH:/usr/local/go/bin:/go/bin \