Mention that files.add has a pin option

[Powersource]

To quote lidel's code in irc:
ipfs.files.add(Buffer.from('auto-pin')).then(results => ipfs.pin.ls(results[0].hash).then(pins => console.dir(pins))).catch(console.error)
vs.
ipfs.files.add(Buffer.from('no-auto-pin'), {pin: false}).then(results => ipfs.pin.ls(results[0].hash).then(pins => console.dir(pins))).catch(console.error)

Should also mention that it automatically pins. (Do I have to add recursively to get it to pin recursively?)

[alanshaw]

@Powersource pin.add has a recursive option - the recursive add does not effect what happens when you pin.

Would you be willing to send a PR to the docs here?

[Powersource]

#297