Use placeholder in search box

Would y'all be amenable to a pull request that changed the search box in the header section of the site to use `placeholder`? Right now, it sets a value of "Search gems..." and I guess use JavaScript to remove it on focus or whatever. I've seen, a couple of times, that the text didn't go away on focus and, well, that's what `placeholder` is for. I haven't dived into the code, but it seems like it'd be a simple change in the template, probably. I don't know about ripping out whatever JS is driving the rest. Thoughts?