Don't download a 129MB file automatically

[adamvoss]

Original report of issue was at webtorrent/webtorrent#815

In my case I am on a usage-caped satellite Internet connection. It is rather hard to visit the website to learn about webtorrent because of the data that will be consumed while I try to read the webpage.

The suggestions proposed by @franciscop on the original issue were:

• Download a 2-3MB file. However this is not so cool as you cannot see the video itself, but much better than using the user's data plan.
• Detect the device/screen and choose to download only on desktop. However this is probably error-phrone.
• Add a "stop" button (or a "start" one) so the visitors can toggle the torrent download at will.

Note: I am not a fan of the second one because there are many cases (such as mine) where you do not want the automatic download on a desktop either.

[feross]

We added the second approach. There is an explicit "start" button if your window size is small enough. I suggest using that. Sorry that there's not a better solution.