Re-write IPLD lessons to new API

[mikeal]

The CBOR API changes have been merged upstream into the latest IPFS. This means we need to:

• Update the version of js-ipfs in the lessons.
• Update the IPLD lessons to use the new API
  • Replace {"/": cid.toBaseEncodedString()} with cid.

[terichadbourne]

@mikeal Are you game to take on fixing the lesson itself, with any instruction changes that are immediately obvious to you, and then I can go back through and proof it for comprehensibility in its new form?

I'll reference the old issue when I do that, as there was some stuff like suggesting a while loop that's unrelated to the change in how the API works.

[mikeal]

I'll do the first pass and then hand it off to you for review and merger.