ensure that npm environmental config gets used

Fixes npm/npm#6483.

/cc @iarna for review / knowledge-sharing @wilmoore because he identified this bug.
Setting the default initial version to `1.0.0` is a tool to help remedy the confusing semantics for semver versions less than 1.0.0. It is a very mild form of social pressure on the npm user base, but I think it's been helpful. Also, @rvagg and @timoxley lobbied pretty hard for that change, so you'd have to convince them before I'd tempt their wrath by changing the default again.