Correct error in Utils.normalize_path that changed paths improperly

We were using Rails 4.0.1rc2 and discovered a bad regular expression in path normalization. This expression:

```ruby
/(%[a-f0-9]{2}+)/
```

Is intended to match percent-encoded characters but, in fact, matches everything until it meets a character that isn't between a-f or 0-9. Removing the plus fixes the problem, so only the two characters immediately following the % will be matched and uppercased. Tests attached.