rename limiter to throttle and refactor

- don't inject raf/setTimeout since we can't really mock them w/ a good degree of timing accuracy anyways

fix some unrelated tests

api/throttle.js

@@ -0,0 +1,23 @@
+"use strict"
+
+module.exports = function(callback) {
+	//60fps translates to 16.6ms, round it down since setTimeout requires int
+	var time  = 16
+	var last = 0, pending = null
+	var timeout = typeof requestAnimationFrame === "function" ? requestAnimationFrame : setTimeout
+	return function(synchronous) {
+		var now = new Date().getTime()
+		var diff = now - last
+		if (synchronous === true || last === 0 || now - last >= time) {
+			last = now
+			callback()
+		}
+		else if (pending === null) {
+			pending = timeout(function() {
+				pending = 0
+				callback()
+				last = new Date().getTime()
+			}, time - (now - last))
+		}
+	}
+}