Deservicify core (#2458)

* De-servicify router (mostly)

Still uses the redraw service, but it no longer has an intermediate
service of its own.

Also, did a *lot* of test deduplication in this. About 30-40% of the
router service tests were already tested on the main router API instance
itself.

Bundle size decreased from 9560 to 9548 bytes min+gzip.

* Merge `m.mount` + `m.redraw`, update router

Simplifies the router and redraw mechanism, and makes it much easier to
keep predictable.

Bundle size down to 9433 bytes min+gzip, docs updated accordingly.

* Make `mithril/render` just return the `m.render` function directly.

* Deservicify `m.render`, revise `m.route`

- You now have to use `mithril/render/render` directly if you want an
  implicit redraw function. (This will likely be going away in v3.)
- Revise `m.route` to only `key` components

* Add `redraw` to `m.render`, deservicify requests

* Test error logging

* Update docs + changelog [skip ci]

api/mount-redraw.js

@@ -0,0 +1,50 @@
+"use strict"
+
+var Vnode = require("../render/vnode")
+
+module.exports = function(render, schedule, console) {
+	var subscriptions = []
+	var rendering = false
+	var pending = false
+
+	function sync() {
+		if (rendering) throw new Error("Nested m.redraw.sync() call")
+		rendering = true
+		for (var i = 0; i < subscriptions.length; i += 2) {
+			try { render(subscriptions[i], Vnode(subscriptions[i + 1]), redraw) }
+			catch (e) { console.error(e) }
+		}
+		rendering = false
+	}
+
+	function redraw() {
+		if (!pending) {
+			pending = true
+			schedule(function() {
+				pending = false
+				sync()
+			})
+		}
+	}
+
+	redraw.sync = sync
+
+	function mount(root, component) {
+		if (component != null && component.view == null && typeof component !== "function") {
+			throw new TypeError("m.mount(element, component) expects a component, not a vnode")
+		}
+
+		var index = subscriptions.indexOf(root)
+		if (index >= 0) {
+			subscriptions.splice(index, 2)
+			render(root, [], redraw)
+		}
+
+		if (component != null) {
+			subscriptions.push(root, component)
+			render(root, Vnode(component), redraw)
+		}
+	}
+
+	return {mount: mount, redraw: redraw}
+}