Adding a PHP placeholder in the guidelines.

This adds a pointer to the MediaWiki guideles as well as a submodule
with their stylize script for PHP and instructions on how to use it.
Changing the title of the using section.
Adding instructions an stylizing before committing.
Copy over the Wikia specific recommendation.

Copied over the Wikia PHP specific guideline from
https://one.wikia-inc.com/wiki/Engineering/Development_Guidelines/Code_Style#PHP.
Fix parameter passing to the stylize wrapper.

I switched to $* to "$@". This is the recommended approach and should
ensure that positional parameters are preserved.

/cc @jnrbsn
Merge pull request #26 from Wikia/php-coding-conventions-githook

Adding a PHP placeholder in the guidelines and MediaWiki stylize script