Allow npm args to be passed in during cozy-light calls

[BigBlueHat]

Something like this (re: a chat with @bnjbvr in #cozycloud earlier):

cozy-light install distro --npm-args="--msvs_version=2012"

I have to add that...because Windows: http://stackoverflow.com/a/22536869/507169

Right now I've added it manually to the npm.js file in roughly this area: https://github.com/cozy-labs/cozy-light/blob/master/lib/helpers/npm.js#L32

But that's less sustainable. :leaves:

[frankrousseau]

Thank you @BigBlueHat. We'll think about it!