Don't use regex to split query string since this doesn't work correctly in IE8

this fixes #552
Just a heads up, might not be a problem. This makes ?foo= be 

```
foo: ''
```

and  ?foo
```
foo: null
```

Before both of these became

```
foo: undefined
```

Could have some unwanted effects, not sure though. Depends how that data is handled further.


I used this in a local patch I made.
```
    var parts = pair.split('='),
      key = parts.shift(),
      rest = parts.join('=') || undefined
      value = rest && decodeURIComponent(rest.replace(/\+/g, ' '));
```