Can we also add this test?

```js
assert.equal(System.normalize('a/b/../c'),'a/b/../c');
assert.equal(System.normalize('a/b/../c', refererName),'a/b/../c');
```

These are not relative so should be passed through as is.

```js
assert.equal(System.normalize('a/../b', refererName),'./dir/b');
```

If we use removeDotSegments then this ends up being relative even though Jason's proposal does not allow '..' except at the beginning. We could throw on this if we wanted to?