always add range header on data request

[fredericgermain]

Hi !

I notice the download was very slow for audio, so I compared with python youtube-dl.
I find out that the youtube server is really slow if the Range: header is missing.
This commit always adds a Range: header

Fixes #251

[Kikobeats]

Awesome, thanks for that!

is this a thing that is related with an specific provider (e.g., YouTube) or potentially could speed up any download?

[fredericgermain]

It's really related to youtube, and maybe only audio downloads? I was only interested in audio and didn't check on video that much, but I don't see any problem on the tests.

This header makes a huge difference on how fast the youtube server send data. But I have no idea why, it shouldn't be necessary from HTTP spec.
It looks like the server makes pauses every ~130672 bytes when no range, so I added 3:20 music video for test. Without the range hack, npm run test takes around 2mins. Sometimes more the 3mins and then the transfer timeout and the test fails. With range header, it's around 40s (the audio download is < 1s).

I also made a commit to fix test on node 12 (and 10). It seems there are still some failures with node 8...

[Kikobeats]

Thanks for the explanation! I want to drop node8 in the next version, stay tuned!

[mayeaux]

Nice work @fredericgermain !

[fredericgermain]

Thanks for the new already available version 3.0.0 ! :)