updated readme

README.md

 slrn lets you select a region or window and ffmpeg will record it in the format of your choice!
 Combined with keybinds and a server on your filesystem you can make a really neat and unobtrusive screenshooter.
 
+You can also take images using imagemagick like so:
+```bash
+#!/bin/bash
+eval `slrn`
+import -window root -crop "$W"x"$H"+$X+$Y ~/myimage.png
+```
+
 lets see some action
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 Ok. Here's a comparison between 'scrot -s's selection and slrn's: