Consider removing ipfs-http-client dependency

The `ipfs-http-client` is one of the largest dependencies of this package and we only use a very small portion of its functionality. It seems pretty straightforward to replace by a few HTTP requests, reducing the size of the bundle.

On the other hand, it's one more moving part we'd have to maintain in order not to let it break in future releases. Truth be told, the HTTP API from IPFS has been pretty stable so it probably wouldn't be a problem immediately.