Thirtydaysago in base.py does not have the right count

[Aurélien]

Hi,

Just a little fix, in the airnotifier/controllers/base.py line 159 you have :

thirtydaysago = now - 60 * 60 * 24 (it's just 24 hours)

But the right count for thirtydays is 60 * 60 * 24 * 30.

It's a pleasure to contribute.

Thank You

[dcai]

Thank you!