feat: Ability to query by time posted for linkedin, indeed, glassdoor

[VitaminB16]

Added argument hours_old to scrape_jobs, which sets the limit for the age of the post.

LinkedIn allows filtering by hours (even seconds), but Glassdoor and Indeed only allow filtering by days – so I am rounding it up to the nearest whole day for those two.

I have not found a way to do this for Ziprecruiter yet.

[cullenwatson]

sweet