Add a "compact" script to the buildpack to reduce final image size. Realized that webpack was always required even though it's a devDep; made it so that it doesn't have to be loaded.

buildpack/buildpacks/node/bin/compact

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+set -e            # fail fast
+set -o pipefail   # don't ignore exit codes when piping output
+# set -x          # enable debugging
+
+# Configure directories
+build_dir=$1
+cache_dir=$2
+env_dir=$3
+
+bp_dir=$(cd $(dirname $0); cd ..; pwd)
+
+# Load some convenience functions like status() and indent()
+source $bp_dir/bin/common.sh
+
+# Output npm debug info on error
+trap cat_npm_debug_log ERR
+
+# Run subsequent node/npm commands from the build path
+cd $build_dir
+
+# Run twice as we may be able to remove a few more dependencies
+# on the second run
+status "Pruning development dependencies"
+npm prune --production --userconfig $build_dir/.npmrc 2>&1 | indent
+npm prune --production --userconfig $build_dir/.npmrc 2>&1 | indent