Download too slow

markdown-preview-macos.tar.gz

I execute the function mkdp#util#install() in vim after finished PlugInstall, but the download speed is very slow even can't download. Btw, I'm in China and opened my network proxy. Then I found the download link and download in chrome. The speed is fast. Then I put it in the correct directory what I get from source code,, everything is fine.

I don't feel very good about installing it.