lifecycle: clean up callback mutation code
slide@1.1.6
style tweaks & dead variable removal
Defer rollbacks to end of install.

This ought to nail the ENOENT issues we're seeing in #6043 by deferring
all rollback unbuilds to the end of the install process. This also
depends on the upgrade to slide@1.1.5.

Includes a test with a very racy optional dependency situation. (*wink*)
reformat test for less oof
pack scoped packages correctly (fixes #6175)
fix relative paths in local dependencies
function name spacing
npm-package-arg@2.1.2

support git+file:// URLs for local bare repos
don't check in node_modules

generalize git check in for non-deployable packages
added links to node.js download page
update changelog for npm@2.0.0
2.0.0
attach the node version to the published document
Disabled `prepublish` when running production mode install.

See discussion in #3059.
use writeFileAtomic instead of fs.writeFile fixes #6163