v2.0.0

BREAKING CHANGES:

• 4378a17
semver@4.0.0: prerelease versions no longer show up in ranges; ^0.x.y
  behaves the way it did in semver@2 rather than semver@3; docs have been
  reorganized for comprehensibility (@isaacs)
• c6ddb64
  npm now assumes that node is newer than 0.6
  (@isaacs)

Other changes:

• ea515c3
  #6043 slide@1.1.6: wait until all
  callbacks have finished before proceeding
  (@othiym23)
• 0b0a59d
  #6043 defer rollbacks until just
  before the CLI exits (@isaacs)
• a11c88b
  #6175 pack scoped packages
  correctly (@othiym23)
• e4e48e0
  #6121 read-installed@3.1.2: don't
  mark linked dev dependencies as extraneous
  (@isaacs)
• d673e41
cmd-shim@2.0.1: depend on graceful-fs directly
  (@ForbesLindesay)
• 9d54d45
npm-registry-couchapp@2.5.3: make tests more reliable on Travis
  (@iarna)
• 673d738
  ensure permissions are set correctly in cache when running as root
  (@isaacs)
• 6e6a5fb
  prepare for upgrade to node-semver@4.0.0
  (@isaacs)
• ab8dd87
  swap out ronn for marked-man@0.1.3 (@isaacs)
• 803da54
npm-registry-client@3.2.0: prepare for node-semver@4.0.0 and include more
  error information (@isaacs)
• 4af0e71
  make default error display less scary (@isaacs)
• 4fd9e79
npm-registry-client@3.2.1: handle errors returned by the registry much,
  much better (@othiym23)
• ca791e2
  restore a long (always?) missing pass for deduping
  (@othiym23)
• ca0ef0e
  correctly interpret relative paths for local dependencies
  (@othiym23)
• 5eb8db2
npm-package-arg@2.1.2: support git+file:// URLs for local bare repos
  (@othiym23)
• 860a185
  tweak docs to no longer advocate checking in node_modules
  (@hunterloftis)
• 80e9033
  add links to nodejs.org downloads to docs
  (@meetar)