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]

request/request.js

@@ -2,9 +2,8 @@
 
 var buildPathname = require("../pathname/build")
 
-module.exports = function($window, Promise) {
+module.exports = function($window, Promise, oncompletion) {
 	var callbackCount = 0
-	var oncompletion
 
 	function PromiseProxy(executor) {
 		return new Promise(executor)
@@ -191,8 +190,5 @@ module.exports = function($window, Promise) {
 				encodeURIComponent(callbackName)
 			$window.document.documentElement.appendChild(script)
 		}),
-		setCompletionCallback: function(callback) {
-			oncompletion = callback
-		},
 	}
 }