Add Notice for those who will install it on Docker containers to add --unsafe-perm on npm install about pylon

[exsilium]

Hi! Thanks for the issue report, can you perhaps add more details how you are currently doing the install on Docker and which node/npm version you are using? Also, what specific errors you get without the --unsafe-perm. I did some containerisation PoC at https://github.com/exsilium/docker-c9v2 but this is on node 6, built on Docker Hub some time ago so it might be an issue I have not yet encountered or affects newer Node versions. Thanks & Cheers! 🙇 🍻

[sr229]

@exsilium I'm using NodeSource's v8.x and I noticed this by building it on Fedora 27. Giving the fact F27 always is the bleeding-edge distribution I took the liberty to use Multi-stage building by building it to Debian then copying the installation to another container. You can find the whole stage on the v2 folder of our docker implementation for Cloud 9.

So before I patched this, I used the one stated in the README. Doing a quick StackOverflow search i was able to find it due to npm trying to lower down it's permissions. This would cause issues on postinstall stage later on. adding --unsafe-perm as a work around is most ideal since it allows NPM to proceed even with high permissions.

I concluded that V8 and above has issues with this but not V6 and below