Merge branch 'hotfix/6576'

Close #6576
Allow running php-cs-fixer in parallel

A recent change in php-cs-fixer has led to massive performance issues, leading
to timeouts of ZF2 builds. This change is a band-aid, and does the following:

- Alters the php-cs-fixer configuration to remove the lines that excluded
  top-level paths, and added paths to test. This means you cannot just run
  "php-cs-fixer" in the root anymore; you **must** pass a directory in which to
  run the checks.
- Alters the Travis-CI configuration to list the directories in which to run
  php-cs-fixer and pass them to the `parallel` command.

The changes ensure that output will occur periodically. The checks run
_somewhat_ faster, though the performance improvement is certainly less than
50%.
Switched to known good revision of php-cs-fixer

- Determined from last build that did not have CS errors flagged.
Updated php-cs-fixer rules

- Path restrictions must be specified differently when you pass the path to a
  component via the CLI as an argument to php-cs-fixer; they become relative to
  the argument, not the project root.
Re-instated two notPath() rules
Merge branch 'hotfix/#6671-fixed-parallelized-cs-checks' into develop

Forward port #6671