Add #process_task to VSE example code

Per the gists linked. Rather than duplicating it in each example.
Internalise two of the VSE examples

Rather than linking out to personal gists. Because Sneha may not keep them
forever, and they should be version controlled here.

The NAT example is missing because GitHub currenlty returns:
```
Hm.

This gist can't be viewed at the moment. Please send a message to Support and we'll have a look as soon as we can.
```

@snehaso, do you have another copy of this?
Merge pull request #99 from alphagov/vse_doc_examples

Internalise two of the VSE examples