Set the default path to composer.lock

So we can call it with 'security-checker s:c'
Ensure the data is present before use it
Replace composer.json by composer.lock to prevent typo
Merge remote-tracking branch 'lyrixx/feat-default-composer-path'

* lyrixx/feat-default-composer-path:
  Replace composer.json by composer.lock to prevent typo
  Ensure the data is present before use it
  Set the default path to composer.lock

Conflicts:
	SensioLabs/Security/SecurityChecker.php