doc: multiple documentation updates cherry picked from v0.12

 * doc: improve http.abort description
 * doc: mention that mode is ignored if file exists
 * docs: Fix default options for fs.createWriteStream()
 * Documentation update about Buffer initialization
 * doc: add a note about readable in flowing mode
 * doc: Document http.request protocol option
 * doc, comments: Grammar and spelling fixes
 * updated documentation for fs.createReadStream
 * Update child_process.markdown, spelling
 * doc: Clarified read method with specified size argument.
 * docs:events clarify emitter.listener() behavior
 * doc: two minor stream doc improvements
 * doc: clarify Readable._read and Readable.push
 * doc: stream.unshift does not reset reading state
 * doc: readable event clarification
 * doc: additional refinement to readable event

Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noorduis <ben@strongloop.com>
PR-URL: https://github.com/nodejs/io.js/pull/2302