new npm-specific update-notifier implementation

This drops our usage of the update-notifier module, in favor of checking
ourselves, using the modules and UX patterns that npm already has in
place.

- While on a prerelease version, updates are checked for every day,
  instead of every week, and always checks for a new beta in the current
  release family.  Ie, ^7.0.0-beta.2 instead of latest.
- Latest version is suggested if newer than current.
- If current version is newer than latest, then we check again for an
  update in the current version family.  Ie, ^7.0.0 instead of latest,
  if current is 7.0.0 and latest is 6.x.
- Output is printed using log.notice, at the end of all other log
  output, so that it's both less visually disruptive, and less likely to
  be missed among other warnings and notices.

This has the side effect of requiring that we set npm.flatOptions as
soon as config is loaded, rather than waiting for a command to be run.
Since the cli runs a command immediately after loading anyway, this is
not a relevant change for our purposes, but worth mentioning here.

1 files changed, 1 insertions, 2 deletions

diff --git a/test/lib/npm.js b/test/lib/npm.js
index e4e31e5d3..3c62643fc 100644
--- a/test/lib/npm.js
+++ b/test/lib/npm.js
@@ -115,8 +115,7 @@ t.test('npm.load', t => {
       t.match(npm, {
         loaded: true,
         loading: false,
-        // flatOptions only loaded when we run an actual command
-        flatOptions: null
+        flatOptions: {}
       })
       t.equal(firstCalled, true, 'first callback got called')
       t.equal(secondCalled, true, 'second callback got called')