[changed] fallback to window.location for history

When `<Routes location=“history”/>` is used
we now fall back to window.location for browsers
that don’t support the HTML5 history API

Rather than falling back to hash, falling back to
window.location ensures urls are identical for
all users, and sharing them will always work

closes #50

modules/stores/URLStore.js

@@ -70,6 +70,9 @@ var URLStore = {
     if (path === _currentPath)
       return;
 
+    if (_location === 'disabledHistory')
+      return window.location = path;
+
     if (_location === 'history') {
       window.history.pushState({ path: path }, '', path);
       notifyChange();
@@ -87,7 +90,9 @@ var URLStore = {
    * to the browser's history.
    */
   replace: function (path) {
-    if (_location === 'history') {
+    if (_location === 'disabledHistory') {
+      window.location.replace(path);
+    } else if (_location === 'history') {
       window.history.replaceState({ path: path }, '', path);
       notifyChange();
     } else if (_location === 'hash') {
@@ -143,10 +148,15 @@ var URLStore = {
       return; // Don't setup twice.
     }
 
+    if (location === 'history' && !supportsHistory()) {
+      location = 'disabledHistory';
+      return;
+    }
+
     var changeEvent = CHANGE_EVENTS[location];
 
     invariant(
-      changeEvent,
+      changeEvent || location === 'disabledHistory',
       'The URL store location "' + location + '" is not valid. ' +
       'It must be either "hash" or "history"'
     );
@@ -185,4 +195,19 @@ var URLStore = {
 
 };
 
+function supportsHistory() {
+  /*! taken from modernizr
+   * https://github.com/Modernizr/Modernizr/blob/master/LICENSE
+   * https://github.com/Modernizr/Modernizr/blob/master/feature-detects/history.js
+   */
+  var ua = navigator.userAgent;
+  if ((ua.indexOf('Android 2.') !== -1 ||
+      (ua.indexOf('Android 4.0') !== -1)) &&
+      ua.indexOf('Mobile Safari') !== -1 &&
+      ua.indexOf('Chrome') === -1) {
+    return false;
+  }
+  return (window.history && 'pushState' in window.history);
+}
+
 module.exports = URLStore;