use terser and clean-css directly

create a sourcemap as well by default

node_modules/.bin/terser

@@ -1 +1,15 @@
-../terser/bin/terser
+#!/bin/sh
+basedir=$(dirname "$(echo "$0" | sed -e 's,\\,/,g')")
+
+case `uname` in
+    *CYGWIN*|*MINGW*|*MSYS*) basedir=`cygpath -w "$basedir"`;;
+esac
+
+if [ -x "$basedir/node" ]; then
+  "$basedir/node"  "$basedir/../terser/bin/terser" "$@"
+  ret=$?
+else 
+  node  "$basedir/../terser/bin/terser" "$@"
+  ret=$?
+fi
+exit $ret