Change EmailValidator::isValid interface

[egulias]

As a first approach, use the Strategy pattern so upon construction EmailValidator requires the strategies objects to be used for validation.
Strategies will be evaluated in an AND fashion. E.g

//$result has been setted after the first validation
foreach ($this->strategies as $strategy) {
  $result = $result && $strategy->isValid($email, $this->lexer, $this->getWarnings());
}

Right now $this->lexer is mutable, probably needs to be immutable so there's no riks while passing it around.
Should also define ValidationStretegy::isValid interface.
RFCs validation would be the only one "hardcoded" within the validator. Probably being added in the constructor.

EmailValidator::__construct(ValidationStrategies $stretegies)