Allow non newest version PHP to install tools.

Installation of PHP tools was blocked if installed PHP does not match to the newest formulas.

It should be allowed for **ANY** PHP including older installation. If not so, `brew upgrade` command would be failed while upgrading.

```
$ brew outdated
php-code-sniffer (1.4.5 < 1.4.6)
php54 (5.4.15 < 5.4.16)
$brew upgrade

```

"Missing PHP53, PHP54 or PHP55 ..." would be shown because first updating `php-code-sniffer` run but current `php54` does not match to `5.4.16`.