Merge branch 'cs/#6995-zend-servicemanager-psr2-compliance'

Close #6995
Composer: Require squizlabs/php_codesniffer
Travis: Run phpcs with PSR-2
Fix: Remove fabpot/php-cs-fixer
Fix: Update README-GIT.md

Remove note about adding Git pre-commit hook.

[skip ci]
Fix: Show phpcs summary report on Travis only

Full report is too long for Travis.
Fix: Use phpcs in GIT pre-commit hook
#6182 - running PHPCS checks in parallel
#6182 - Excluding paths (as of `.php_cs`)
#6182 - Can actually use `"squizlabs/php_codesniffer": "~2.0.0@RC"