normalize file path key to make it work on windows

release after `0.7.11` seems to have broken nap on windows.

Here are the fixes for windows. (It now works on windows. also tested with mac and seems to work fine.)

Not adding `path.normalize` seems to break windows.

```
ENOENT, no such file or directory 'C:\dumps\test\C:\dumps\test\public\stylesheets\_vendor\bootstrap.min.css'
```

replacing the key is required so `\` gets rendered as `/` in `href` as well as JST key.

```html
 <link href='/assets/public\stylesheets\_vendor\bootstrap.min.css' rel='stylesheet' type='text/css'>
```

```js
JST['\admin\index'] = "....";
```