adding readme for lab 6 version of app

lab-6/music-store-app/README.txt

+Live Demo
+---------
+A live deployment of this app can be viewed at:
+http://doc.gold.ac.uk/~sharr003/dnw/lab-6/music-store-app/
+
+Configuration
+-------------
+- Create a blank MySQL database
+- Run the statements in sql/schema.sql on your MySQL database to set up the app schema
+- Run the statements in sql/dummy-data.sql on your MySQL database to insert some dummy data (optional)- Edit includes/db_connect.php with your database connection details