Limit version of php-cs-fixer >= 3.4.0 <= 3.5.0

[vladvildanov]

Php-cs-fixer package continue constantly updating, so are codestyle rules. This leads often to CI failures and requires separate PR so it won't be mixed with actual changes. I propose to limit to the latest minor version, to avoid this codestyle changes and lately we have to choose more stable version.

[coveralls]

coverage: 92.613%. remained the same
when pulling 78f7cba on vladvildanov:vv-limit-php-fixer-version
into 40d72d7 on predis:main.