Expose cause for EmailVerifier::OutOfMailServersException

[g0ody]

We needed the internal reason why EmailVerifier::OutOfMailServersException was caused. If retry is used rubies nested exceptions do not work.

begin
  EmailVerifier.check(email)
rescue EmailVerifier::OutOfMailServersException => e
  p e.cause
end

[adamof]

Hey @g0ody, we're having some issues, since we are receiving this exception for emails that are actually valid. Can you explain how your change affects the behaviour of the gem?

[g0ody]

Before it raise the EmailVerifier::OutOfMailServersException when servers are nil. This was caused by the retry. But this way you use the cause EmailVerifier::OutOfMailServersException, that is provided by ruby automatically if you raise an exception in a rescue function.

So I restructure the call so that the exception is raised in the rescue function, to be able to access the original execption when EmailVerifier::OutOfMailServersException is raised.

Other than that the behaviour stays the same.