Deleted redundant test
It ignores invalid email addresses
Separated the filtering of valid emails from the splitting
Refactor extracted helper method and renamed another method
It ignores duplicate email addresses
Refactor: Extracted duplicate email addresses removal to a helper method
Refactor: Generalized duplicate elements removal for vectors of any type and moved it to VectorUtils
Refactor: Extracted explaining helper
Refactor: Now using copy_if algorithm
Changed filter so it can works with std::bind1st y std::mem_fun