Deduplicate m.route and m.redraw logic (#2453)

- Remove appropriate route change subcriptions when a root is removed
  via `m.mount(root, null)`.
- Don't pollute `onpopstate` and friends - use standard event listeners
  instead.
- Simplify and streamline subscriptions, in preparation of adding a
  `remove` parameter to `m.mount`.
- Change the redraw internals to redraw immediately, with ability to
  cancel via returning a sentinel.
- Change `"bleeding-edge"` for `m.version` in `next` to instead just be
  the latest `m.version`. (If you're using `next`, you should know what
  you're in for.)
- Update tests to be aware of these changes. (Some were failing for
  subtle reasons.)
- Drive-by: remove some uses of `string.charAt(n)` and use `string[n]`
  instead.

router/tests/test-getPath.js

@@ -10,6 +10,10 @@ o.spec("Router.getPath", function() {
 			o.spec("using prefix `" + prefix + "` starting on " + env.protocol + "//" + env.hostname, function() {
 				var $window, router, onRouteChange, onFail
 
+				function defineRoutes(routes, defaultRoute) {
+					router.defineRoutes(routes, onRouteChange, onFail, defaultRoute, function() {})
+				}
+
 				o.beforeEach(function() {
 					$window = pushStateMock(env)
 					router = new Router($window)
@@ -20,25 +24,25 @@ o.spec("Router.getPath", function() {
 
 				o("gets route", function() {
 					$window.location.href = prefix + "/test"
-					router.defineRoutes({"/test": {data: 1}}, onRouteChange, onFail)
+					defineRoutes({"/test": {data: 1}})
 
 					o(router.getPath()).equals("/test")
 				})
 				o("gets route w/ params", function() {
 					$window.location.href = prefix + "/other/x/y/z?c=d#e=f"
-					router.defineRoutes({"/test": {data: 1}, "/other/:a/:b...": {data: 2}}, onRouteChange, onFail)
+					defineRoutes({"/test": {data: 1}, "/other/:a/:b...": {data: 2}})
 
 					o(router.getPath()).equals("/other/x/y/z?c=d#e=f")
 				})
 				o("gets route w/ escaped unicode", function() {
 					$window.location.href = prefix + "/%C3%B6?%C3%B6=%C3%B6#%C3%B6=%C3%B6"
-					router.defineRoutes({"/test": {data: 1}, "/ö/:a/:b...": {data: 2}}, onRouteChange, onFail)
+					defineRoutes({"/test": {data: 1}, "/ö/:a/:b...": {data: 2}})
 
 					o(router.getPath()).equals("/ö?ö=ö#ö=ö")
 				})
 				o("gets route w/ unicode", function() {
 					$window.location.href = prefix + "/ö?ö=ö#ö=ö"
-					router.defineRoutes({"/test": {data: 1}, "/ö/:a/:b...": {data: 2}}, onRouteChange, onFail)
+					defineRoutes({"/test": {data: 1}, "/ö/:a/:b...": {data: 2}})
 
 					o(router.getPath()).equals("/ö?ö=ö#ö=ö")
 				})