Compare location changes against initialState.

Also, replace the location, rather than transitionTo it.

The location in the initialState is no longer undefined, so we should compare if we're going back to that state. Because the initial action is normally a POP, we can't transition to that kind of action and instead need to replace our location.

Fixes #164
Fixes #252

src/index.js

@@ -83,8 +83,8 @@ export function syncHistory(history) {
         // If we're resetting to the beginning, use the saved initial value. We
         // need to dispatch a new action at this point to populate the store
         // appropriately.
-        if (!location) {
-          history.transitionTo(initialLocation)
+        if (location.key === initialLocation.key) {
+          history.replace(initialLocation)
           return
         }