chore: add NPM publishing on Travis-CI

[nschonni]

Closes #231

[XhmikosR]

Your patch no longer tests on v0.10 which is supported in theory. Otherwise it should be changed in package.json and any other places.

Other than that, it's your call if you want to do this automatically. :)

[nschonni]

I can add it back, but it did EOL back in October

[XhmikosR]

Just to be clear, I don't care about 0.10 :) Just make sure the drop is proper and mentioned everywhere.

[XhmikosR]

@nschonni: my only 2 concerns:

1. I'd go with numbers instead of aliases because it's clearer which is what
2. We need to update package.json engines property for the node < 4 drop (and any other places)

[nschonni]

@frvge sorry, I just saw that you've been landing stuff again :) I'll try and fix this up and do the same for CSSLint so i'm not a blocker for getting stuff out. /cc @stubbornella

[frvge]

@nschonni , can we get this one out the door in 2018?