2016-04-26, Version 6.0.0 (Current) Release

The following significant (semver-major) changes have been made since the
previous Node v5.0.0 release.

* Buffer
  * New Buffer constructors have been added
    [nodejs#4682](nodejs#4682)
  * Previously deprecated Buffer APIs are removed
    [nodejs#5048](nodejs#5048),
    [nodejs#4594](nodejs#4594)
  * Improved error handling [nodejs#4514](nodejs#4514)
* Cluster
  * Worker emitted as first argument in 'message' event
    [nodejs#5361](nodejs#5361).
* Crypto
  * Improved error handling [nodejs#3100](nodejs#3100),
    [nodejs#5611](nodejs#5611)
  * Simplified Certificate class bindings
    [nodejs#5382](nodejs#5382)
  * Improved control over FIPS mode
    [nodejs#5181](nodejs#5181)
  * pbkdf2 digest overloading is deprecated
    [nodejs#4047](nodejs#4047)
* Dependencies
  * Reintroduce shared c-ares build support
    [nodejs#5775](nodejs#5775).
  * V8 updated to 5.0.71.31 [nodejs#6111](nodejs#6111).
* DNS
  * Add resolvePtr API to query plain DNS PTR records
    [nodejs#4921](nodejs#4921).
* Domains
  * Clear stack when no error handler
  [nodejs#4659](nodejs#4659).
* File System
  * The `fs.realpath()` and `fs.realpathSync()` methods have been updated
    to use a more efficient libuv implementation. This change includes the
    removal of the `cache` argument and the method can throw new errors
    [nodejs#3594](nodejs#3594)
  * FS apis can now accept and return paths as Buffers
    [nodejs#5616](nodejs#5616).
  * Error handling and type checking improvements
    [nodejs#5616](nodejs#5616),
    [nodejs#5590](nodejs#5590),
    [nodejs#4518](nodejs#4518),
    [nodejs#3917](nodejs#3917).
  * fs.read's string interface is deprecated
    [nodejs#4525](nodejs#4525)
* HTTP
  * 'clientError' can now be used to return custom errors from an
    HTTP server [nodejs#4557](nodejs#4557).
* Modules
  * Current directory is now prioritized for local lookups
    [nodejs#5689](nodejs#5689)
  * Symbolic links are preserved when requiring modules
    [nodejs#5950](nodejs#5950)
* Net
  * DNS hints no longer implicitly set
    [nodejs#6021](nodejs#6021).
  * Improved error handling and type checking
    [nodejs#5981](nodejs#5981),
    [nodejs#5733](nodejs#5733),
    [nodejs#2904](nodejs#2904)
* OS X
  * MACOSX_DEPLOYMENT_TARGET has been bumped up to 10.7
    [nodejs#6402](nodejs#6402).
* Path
  * Improved type checking [nodejs#5348](nodejs#5348).
* Process
  * Introduce process warnings API
    [nodejs#4782](nodejs#4782).
  * Throw exception when non-function passed to nextTick
    [nodejs#3860](nodejs#3860).
* Readline
  * Emit key info unconditionally
    [nodejs#6024](nodejs#6024)
* REPL
  * Assignment to `_` will emit a warning.
    [nodejs#5535](nodejs#5535)
* Timers
  * Fail early when callback is not a function
    [nodejs#4362](nodejs#4362)
* TLS
  * Rename 'clientError' to 'tlsClientError'
    [nodejs#4557](nodejs#4557)
  * SHA1 used for sessionIdContext
    [nodejs#3866](nodejs#3866)
* TTY
  * Previously deprecated setRawMode wrapper is removed
    [nodejs#2528](nodejs#2528).
* Util
  * Changes to Error object formatting
    [nodejs#4582](nodejs#4582).
* Windows
  * Windows XP and Vista are no longer supported
    [nodejs#5167](nodejs#5167),
    [nodejs#5167](nodejs#5167).

Author: jasnell