IE7 gains an extra slash when using the default constructor

If you head to http://medialize.github.com/URI.js/ and use the default constructor, you get:

```
>> new URI().href() 
"http://medialize.github.com/URI.js/"
```

If you run it in IE7 (or in this case, IE9 in IE7 mode), you get:

```
>> new URI().href() 
"http://medialize.github.com//URI.js/" 
```

Note the double slash after github.com.
