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.

bundler/tests/test-bundler.js

@@ -4,6 +4,7 @@ var o = require("../../ospec/ospec")
 var bundle = require("../bundle")
 
 var fs = require("fs")
+var pkg = require("../../package.json")
 
 var ns = "./"
 function write(filepath, data) {
@@ -319,4 +320,11 @@ o.spec("bundler", function() {
 		remove("a.js")
 		remove("b.js")
 	})
+	o("reads package.json keys", function() {
+		write("a.js", 'var b = require("./package.json").version')
+
+		o(bundle(ns + "a.js")).equals(";(function() {\nvar b = " + JSON.stringify(pkg.version) + "\n}());")
+
+		remove("a.js")
+	})
 })