".edu" substring is not a good signal to identify if a domain is an university

[mudongliang]

    if not ".edu" in domain:
        continue

This ".edu" is an identifier to classify university domain, but this is not always true in the real world.

The solution:

• Write a function to identify if the domain in the email is in the university domain list [1].

[1] https://github.com/Hipo/university-domains-list

[mudongliang]

I finished the function, and would push a PR today or tomorrow