Streams with writev allow many buffers to be pushed to underlying OS
APIs in one batch, in this case improving write throughput by an order
of magnitude. This is especially noticeable when writing many (small)
buffers.

PR-URL: #2167
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

Notable changes:

* buffer:
  - Buffers are now created in JavaScript, rather than C++. This increases the speed of buffer creation (Trevor Norris) nodejs#2866.
  - `Buffer#slice()` now uses `Uint8Array#subarray()` internally, increasing `slice()` performance (Karl Skomski) nodejs#2777.
* fs:
  - `fs.utimes()` now properly converts numeric strings, `NaN`, and `Infinity` (Yazhong Liu) nodejs#2387.
  - `fs.WriteStream` now implements `_writev`, allowing for super-fast bulk writes (Ron Korving) nodejs#2167.
* http: Fixed an issue with certain `write()` sizes causing errors when using `http.request()` (Fedor Indutny) nodejs#2824.
* npm: Upgrade to version 2.14.3, see https://github.com/npm/npm/releases/tag/v2.14.3 for more details (Kat Marchán) nodejs#2822.
* src: V8 cpu profiling no longer erroneously shows idle time (Oleksandr Chekhovskyi) nodejs#2324.
* v8: Lateral upgrade to 4.5.103.33 from 4.5.103.30, contains minor fixes (Ali Ijaz Sheikh) nodejs#2870.
  - This fixes a previously known bug where some computed object shorthand properties did not work correctly (nodejs#2507).

Refs: nodejs#2844
PR-URL: nodejs#2889

Notable changes:

* buffer:
  - Buffers are now created in JavaScript, rather than C++. This increases the speed of buffer creation (Trevor Norris) #2866.
  - `Buffer#slice()` now uses `Uint8Array#subarray()` internally, increasing `slice()` performance (Karl Skomski) #2777.
* fs:
  - `fs.utimes()` now properly converts numeric strings, `NaN`, and `Infinity` (Yazhong Liu) #2387.
  - `fs.WriteStream` now implements `_writev`, allowing for super-fast bulk writes (Ron Korving) #2167.
* http: Fixed an issue with certain `write()` sizes causing errors when using `http.request()` (Fedor Indutny) #2824.
* npm: Upgrade to version 2.14.3, see https://github.com/npm/npm/releases/tag/v2.14.3 for more details (Kat Marchán) #2822.
* src: V8 cpu profiling no longer erroneously shows idle time (Oleksandr Chekhovskyi) #2324.
* v8: Lateral upgrade to 4.5.103.33 from 4.5.103.30, contains minor fixes (Ali Ijaz Sheikh) #2870.
  - This fixes a previously known bug where some computed object shorthand properties did not work correctly (#2507).

Refs: #2844
PR-URL: #2889