A couple of copyedits:

• Re-orders stream_iter in the TOC.
• Correct Writer method/property indentation below the interface description.
• Move zlib_iter definitions to zlib.md – this one is a YMMV, but there really aren't that many methods here, and the list isn't likely to expand. This seems like it would fit just fine in the parent .md, like the promises submodules do.