This commit makes `os.tmpdir()` behave consistently on all platforms. It
changes `os.tmpdir()` to always return a path without trailing slash.

Semver: major
Fixes: #715
PR-URL: #747
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

PR-URL: #1532

Notable Changes:

* crypto: significantly reduced memory usage for TLS (Fedor Indutny & Сковорода
  Никита Андреевич) #1529
* net: socket.connect() now accepts a 'lookup' option for a custom DNS
  resolution mechanism, defaults to dns.lookup() (Evan Lucas) #1505
* npm: Upgrade npm to 2.9.0. See the v2.8.4 and v2.9.0 release notes for
  details. Notable items:
  - Add support for default author field to make npm init -y work without
    user-input (@othiym23) npm/npm/d8eee6cf9d
  - Include local modules in npm outdated and npm update (@ArnaudRinquin)
    npm/npm#7426
  - The prefix used before the version number on npm version is now configurable
    via tag-version-prefix (@kkragenbrink) npm/npm#8014
* os: os.tmpdir() is now cross-platform consistent and will no longer returns a
  path with a trailling slash on any platform (Christian Tellnes) #747
* process:
  - process.nextTick() performance has been improved by between 2-42% across the
    benchmark suite, notable because this is heavily used across core (Brian White) #1548
  - New process.geteuid(), process.seteuid(id), process.getegid() and
    process.setegid(id) methods allow you to get and set effective UID and GID
    of the process (Evan Lucas) #1536
* repl:
  - REPL history can be persisted across sessions if the NODE_REPL_HISTORY_FILE
    environment variable is set to a user accessible file,
    NODE_REPL_HISTORY_SIZE can set the maximum history size and defaults to 1000
    (Chris Dickinson) #1513
  - The REPL can be placed in to one of three modes using the NODE_REPL_MODE
    environment variable: sloppy, strict or magic (default); the new magic mode
    will automatically run "strict mode only" statements in strict mode
    (Chris Dickinson) #1513
* smalloc: the 'smalloc' module has been deprecated due to changes coming in V8
  4.4 that will render it unusable
* util: add Promise, Map and Set inspection support (Christopher Monsanto) #1471
* V8: upgrade to 4.2.77.18, see the ChangeLog for full details. Notable items:
  - Classes have moved out of staging; the class keyword is now usable in strict
    mode without flags
  - Object literal enhancements have moved out of staging; shorthand method and
    property syntax is now usable ({ method() { }, property })
  - Rest parameters (function(...args) {}) are implemented in staging behind the
    --harmony-rest-parameters flag
  - Computed property names ({['foo'+'bar']:'bam'}) are implemented in staging
    behind the --harmony-computed-property-names flag
  - Unicode escapes ('\u{xxxx}') are implemented in staging behind the
    --harmony_unicode flag and the --harmony_unicode_regexps flag for use in
    regular expressions
* Windows:
  - Random process termination on Windows fixed (Fedor Indutny) #1512 / #1563
  - The delay-load hook introduced to fix issues with process naming (iojs.exe /
    node.exe) has been made opt-out for native add-ons. Native add-ons should
    include 'win_delay_load_hook': 'false' in their binding.gyp to disable this
    feature if they experience problems . (Bert Belder) #1433
* Governance:
  - Rod Vagg (@rvagg) was added to the Technical Committee (TC)
  - Jeremiah Senkpiel (@Fishrock123) was added to the Technical Committee (TC)