sassResolve need normalize

Check https://github.com/xzyfer/gulp-sass-graph/blob/master/index.js#L79

``` javascript
var scssPath = loadPaths[p] + "/" + path + ".scss"
```

if css is `@import "./abc"`
then `path=="./abc"`
then `scssPath=="lib/./abc.scss"` which should be `"lib/abc.scss"`

So code should be:

``` javascript
var scssPath = path.normalize(loadPaths[p] + "/" + path + ".scss")
```
