Use debian:jessie as docker base image

  le                  latest              e1f2e8ce3a0e        14 minutes ago      780.2 MB
vs
  le                  latest              d3276dd3976c        About a minute ago   393.6 MB

where:
  buildpack-deps      jessie              ecff3a5a9760        12 days ago          677.4 MB
  debian              jessie              41b730702607        13 days ago          125.1 MB

Dockerfile

@@ -1,4 +1,4 @@
-FROM buildpack-deps:jessie
+FROM debian:jessie
 MAINTAINER Jakub Warmuz <[email protected]>
 
 # You neccesarily have to bind to 443@host as well! (ACME spec)