Revert "Add PHP_Codesniffer to require"

[zlik]

Reverts #54

[zlik]

Actually, I double checked and PHP_CodeSnifeer will be installed on the project level even if it was already installed globally:

$ ~/.composer/vendor/bin/phpcs -i
The installed coding standards are MySource, PEAR, PSR1, PSR2, Squiz and Zend
$ composer require magento-ecg/coding-standard 3.1
./composer.json has been created
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Installing squizlabs/php_codesniffer (3.0.1)
    Loading from cache

  - Installing magento-ecg/coding-standard (3.1)
    Loading from cache

Writing lock file
Generating autoload files

I would like everyone to always install PHPCS globally in their dev enviroments because this is a widely used development tool. Doing so acknowledges the importance of reusability and prevents duplicating components between dev projects.