Cannot download sketch with large files

Nature of issue?

• Found a bug
• Existing feature enhancement
• New feature request

Details about the bug:

• Web browser and version: Opera 52.0/Safari 11.1
• Operating System: MacOSX 10.13.4
• Steps to reproduce this:
  When I attempt download on a sketch with a large amount of files, I get an error 504, "Gateway Time-out". This happens with sketches such as this one.

[catarak]

thanks for submitting this! i'm able to reproduce. maybe this has to do with trying to create the zip file synchronously?