Add new sort option of Trending

[joshberry]

It would be nice to have an additional sort option of "Trending" added to the sort by drop-down list. This would allow users to view packages that have the most, recent download activity.

I frequently use the "Recent" sort by option to review newer packages but find myself wading through a lot of packages that have very few downloads. A "Trending" sort option would allow gallery users to quickly see what packages are hot.

Not sure exactly how to weight packages for this sort order. It should take into account the recency of downloads.

Any suggestions on how to calculate weighting?

[bhuvak]

Linking to #1296

[loic-sharma]

This could be used to rank search results.