Breaking changes

• Dropped support for Node.js 4 (d73885c).
• Added a shim that throws an error when used if the package is bundled for the
  browser (#1345).
• Added a maxPayload option on the client. Defaults to 100 MiB (#1402).
• Dropped support for the memLevel and level options. Use
  zlibDeflateOptions instead. (80e2002).