Evaluate yarnpkg as a dependency management tool

[jasonblais]

Evaluate yarnpkg as a dependency management tool: https://github.com/yarnpkg/yarn/releases

Should first wait until v1.0.0 is released

[yuya-oc]

mattermost/mattermost#6226 would be good case to watch.

[jasonblais]

Some comments/discussion on pre-release too: https://pre-release.mattermost.com/core/pl/wp8wauuq83gufjhcyahkh67sey

[jasonblais]

Closed via #585

[jasonblais]

FYI @yuya-oc - the platform team is considering to switch back to npm: https://pre-release.mattermost.com/core/pl/t5wbit4k5id4up6btm3qaz13xy

[jasonblais]

@yuya-oc For context:

We're going to be switching the mattermost-webapp, mattermost-mobile, 
and mattermost-redux repositories to use npm instead of yarn because of 
some issues that we've been experiencing with yarn's caching behaviour.
If you're using the Makefiles in those repositories, you shouldn't be affected
other than having to install npm if it isn't already installed.

This may not affect us, but wanted to give a heads up to you in case we want to re-consider npm for the desktop repo.

[yuya-oc]

@jasonblais Thanks to let me know. Right now, we should not back to npm to keep current dependencies until we release v4.1.0. However it's not bad because we can reduce an amount of tools.

[jasonblais]

@yuya-oc Makes sense. Would you recommend we still move away from yarn to npm?

[yuya-oc]

@jasonblais It's hard to say. Actually we don't have any problem in yarn, so either is fine.

In the first time of this issue, yarn was blazing-faster than npm, and could lock all dependencies. That was very important for us. But right now, npm can lock dependencies as well.