added hour_range_enhancement in order to use time window feature

[abirunity]

Hi @johnsusek
My name is Abir and I am working with Praeco in my company (I am working with @osherdp if you remember him).
We wanted to send alerts only at ranged time during the day, so we developed a feature for Praeco.
The feature is called Time Window and the user can use it to send alerts only during specific time range.

I opened a pull request for Praeco: johnsusek/praeco#301
The feature in the mentioned pull request depends on the enhancement I added to elastalert_module in elastalert.
Please review the changes and merge it to Praeco so everyone will be able to use it.

Credits:
@abirsigron - my presonal account
@0xSeb for writing the enhancement: https://github.com/0xSeb/elastalert_hour_range

[nsano-rururu]

Thank you very much for this pull request!