sales.json:
- update date format so it can be sortable
- add more test records (10 in total)
- remove the flow attribute as it is defined in the code
- add a sale's identifier (id)

client.js:
- remove xs.set for the columns variable initialisation
- remove the by_date declaration and initialisation as they are useless
- filter by year as documented

index.html:
- Modify the page title
- use a div tag called 'sales_table' instead of a table tag in the body section

server.js:
- cleanup indentation
- remove unused code
- set sales flow directly using the configuration pipelet (as shown in the documenation)