Reuse js-ipfs-api as IPFS HTTP API client

[lidel]

js-ipfs-api seems to be mature enough to be included as an external dependency responsible for all interactions with IPFS HTTP API.

Ideas:

• A browserified version is already provided:
  • https://npmcdn.com/ipfs-api@9.0.0/dist/index.js
  • https://ipfs.io/ipfs/QmP3fUQAVpvbP3pM47byDa3QRsUbvMztk1F48UU85kgGSW
• Instead of including it in repository, we should just load it from external URL with SRI hash as a fail-safe

[lidel]

Well, PoC works, there are some issues but those will be tracked in #152