Issue #2546272 by hussainweb, jhedstrom, dawehner: Update guzzlehttp/psr7 to 1.2.0 and guzzlehttp/promises to 1.0.2

Issue #2498599 by Cottser, naveenvalecha, webchick, karolus, cilefen: Remove sdboyer/gliph since it is unused by core

Issue #2493911 by dawehner, larowlan, damiankloip, hussainweb, jibran, cilefen, benjy, iMiksu, mtdowling: Update guzzle, goutte and mink-goutte-driver to the latest release

This reverts commit e3391535.

Issue #2343035 by fago, dawehner, larowlan, ianthomas_uk, cilefen, hussainweb, Miroling, jibran, beejeebus, dashaforbes, webmozart, klausi: Upgrade validator integration for Symfony versions 2.5+

Issue #2429363 by babruix, twistor, filijonka, sun, Mile23, daffie, Wim Leers, chx: Add HTML5-lib to Drupal 8 core for the filter system and for the testing system

Issue #2433009 by hussainweb, grom358, neclimdul, daffie, larowlan, alexpott, pcambra, benjy, jibran, phenaproxima, moshe weitzman, nick_schuch: Add Mink, with Goutte driver, to core

Revert "Issue #2433009 by hussainweb, grom358, daffie, larowlan, alexpott, pcambra, benjy, jibran, phenaproxima, moshe weitzman, nick_schuch: Add Mink, with Goutte driver, to core"

This reverts commit 2b96082d.

Issue #2433009 by hussainweb, grom358, daffie, larowlan, alexpott, pcambra, benjy, jibran, phenaproxima, moshe weitzman, nick_schuch: Add Mink, with Goutte driver, to core

Issue #2253593 by neclimdul, damiankloip: Stop classloader searching filesystem for classes before drupal_classloader() is called

Issue #2375997 by Mile23, hussainweb, tstoeckler, omers: Avoid tying Drupal 8's composer.json to specific package commits

Issue #1975220 by davidwbarratt, tstoeckler, mradcliffe, RobLoach, Mile23, hussainweb: Allow a Composer user to manage Drupal, modules, and PHP dependencies with a custom root composer.json