Update to zend-feed 2.7.0

Refiling, thanks! (I'm not sure when we start accepting 8.1 patches...)

I am marking this a "Task" because it is more of something we ought to do than a feature.

@Crell Some limited things are being committed to 8.1.x and cherry-picked to 8.0.x.

This should be a novice task

composer update zendframework/zend-feed --with-dependencies
Updating dependencies (including require-dev)
- Removing zendframework/zend-hydrator (1.0.0)
- Removing zendframework/zend-escaper (2.5.1)
- Installing zendframework/zend-escaper (2.5.2)
Loading from cache

> Drupal\Core\Composer\Composer::vendorTestCodeCleanup
- Removing zendframework/zend-stdlib (2.7.5)
- Installing zendframework/zend-stdlib (3.0.1)
Loading from cache
composer update NOTHING

See changes of updated zendframework/zend-stdlib version:
https://github.com/zendframework/zend-stdlib/releases/tag/release-3.0.0

zend-feed 2.7.0 requires zend-stlib "^2.7 || ^3.0". However, zend-stlib 3.1.0, released today, requires php 5.6.

Now, when I run composer install using php 5.5.9, which is the minimum requirements for Drupal 8, I get this error:

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for zendframework/zend-stdlib 3.1.0 -> satisfiable by zendframework/zend-stdlib[3.1.0].
    - zendframework/zend-stdlib 3.1.0 requires php ^5.6 || ^7.0 -> your PHP version (5.5.9) does not satisfy that requirement.
  Problem 2
    - zendframework/zend-stdlib 3.1.0 requires php ^5.6 || ^7.0 -> your PHP version (5.5.9) does not satisfy that requirement.
    - zendframework/zend-feed 2.7.0 requires zendframework/zend-stdlib ^2.7 || ^3.0 -> satisfiable by zendframework/zend-stdlib[3.1.0].
    - Installation request for zendframework/zend-feed 2.7.0 -> satisfiable by zendframework/zend-feed[2.7.0].

If we explicitly require zend-stdlib 3.0 < 3.1 in composer.json, that should cause composer to resolve to the 3.0.x version of stdlib, shouldn't it? As that would satisfy both that requirement and the transitive requirement through zend-feed.

In patch #9 zend-stdlib was updated to 3.01 only and that version requires php >= 5.5 like Drupal (5.5.9).
If you use composer install the version defined in composer.lock will be installed and you don't have any trouble. By using composer update with specified package only (composer update zendframework/zend-feed / patch #7) dependencies of this package won't updated. Without explicitly require zend-stdlib 3.0 < 3.1 the requirements are satisfied.

The difference is that I'm building a Drupal distro, so my composer.json file "requires" the install profile. Since composer.lock files aren't inherited, Drupal's composer.lock file isn't considered and it tries to pull in v3.1.0 of zend-stdlib.