Homepage refresh 2.0

You can see all of the remaining issues/enhancements that I have planned here: https://github.com/cid-harvard/atlas-economic-complexity/milestones/Homepage%20Final%20Sprint

The two major ones that could be considered important to finish before we deploy are fixing the homepage search analytics tracking, and changing the carousel images per Marcela's requests. But I consider both enhancements/don't want to hold this up any longer/want to get into the practice of deploying more incrementally and often.

The other thing to note is that I've implemented Gulp here to concat/uglify/minify the static resources on the homepage. I'd like to go over those changes with you, @makmanalp, to make sure they make sense and will work on prod.