Add asciicast demo

Author: pimterry

README.md

@@ -1,6 +1,8 @@
 # notes [![Travis Build Status](https://img.shields.io/travis/pimterry/notes.svg)](https://travis-ci.org/pimterry/notes)
 Simple delightful command-line note taking
 
+[![Asciicast demo](asciicast.gif)](https://asciinema.org/a/2pmdb9vyv71skgwx4r7mlnea8?speed=2&t=1&autoplay=1)
+
 ## Why do I want this?
 
 You already have a tool that backs up and syncs your data (be it Dropbox, iCloud, Seafile or whatever). You already have a text editor on your desktop, your laptops, your phone and that tablet you've forgotten about. You want to take notes on these myriad fancy boxes.