Multipart decoding

[lucacorti]

Hey @tomtaylor, great work!

Do you think/would consider a PR adding support for multipart decoding? I can't seem to find any elixir implementations suitable for use with an HTTP client to decode multipart responses and I'm stuck with hackney ATM.

[tomtaylor]

@lucacorti definitely - it's not been a priority for us, but I'm sure it would be useful.

[lucacorti]

I've opened #16 which adds a simple decoding function (e.g. it does not support streaming, only a binary body).