Don't create history state when adding leading slash to hash

Request Type: bug

How to reproduce: 

Component(s): $location

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**

When hash doesn't starts with '/' Angular adds it. This creates new history state in browser. After this window.history.back() and so the back button of browser don't work as expected.

**Other Comments:**