Use a diffing algorithm to show store mutation

[clmntcrl]

Use Mirror to create a string representation of the AppState before and after dispatching action to reducers. Then create a string representation of the difference, and log it.

1. Mirroring step should do its best to make output deterministic by stripping out pointer memory addresses, sorting non-deterministic data (like dictionaries, sets, ...), hide func and closure.

2. Diffing representation could looks like Github unified view for commits, stating line with a + for additions, - for deletions and   if nothing has changed.