Bump to phpcs v3

[razvanphp]

This supersedes #32 by removing the custom Sniffs completely, replaced with Squiz ones, which in turn allows us to bump to phpcs version 3.

It also solves the double quotes missing warning on v3 & removes the need for extra space after php alternate syntax.

Hope to get this merged, thank you!

[mikk150]

find more code style errors as previous one.. pretty good

[samdark]

Merged. Thanks!