added a script to compress PNG

war/images/compress_png.sh

+#!/bin/bash
+
+function compress {
+  echo "Crushing $1"
+  pngcrush -rem gAMA -rem cHRM -rem iCCP -rem sRGB $1 $1.tmp
+  mv $1.tmp $1
+  echo "Compressing $1"
+  optipng -o9 $1 > /dev/null
+}
+
+if [ -z "$*" ]
+then
+  echo 'Please pass a list of pngs to compress.';
+fi
+
+for image in "$@"  # Doesn't work properly if "$*" isn't quoted.
+do
+  compress $image
+done
+