Added new method get_errors_array() to return the errors as key value pairs.

By calling get_errors_array() it returns an array which could be access as follows:

$errors = $gump->get_errors_array();
echo $errors['username'];
echo $errors['password'];

Obviously this limits the errors per field to one single error at a time.
Merge pull request #55 from u12206050/patch-1

Added new method get_errors_array() to return the errors as key value pa...