New "hot" algorithm on homepage

It's a mix between the algorithm that Hacker News and Reddit use.

Prior to this change, the default was just "active" questions. i.e. Any update to a question listed it first on the homepage.

"Active" was fine in the beginning, but as the traffic has grown, so has attempts to spam the site. This algorithm fixes that issue and features the more interesting (and fresh) content first.

The is one downside: Some new questions won't make it to the homepage until they're either upvoted or a good answer is posted to a new question (the answer has to have an upvote too).

Lets test this out for a week and we'll tweak it as needed.