Typo in Demo html

Not a major issue, but there are some typos in the demo html that prevents the Backbone.validateAll from working. 

``` bash
<sript src='../src/javascript/Backbone.validateAll.js'></script>
```

should be

``` bash
<script src='../src/javascripts/Backbone.validateAll.js'></script>
```

There is a missing "c" from the opening script tag and a missing "s" at the end of the javascript folder.
