remove container class

The bbGrid display error when I add bootstrap-responsive.css link.

css: 
```
...
<link rel="stylesheet" href="stylesheets/bbGrid.css" />
<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap-responsive.css" />
```

html:
```
<div class="row">
  <div class="span4">left</div>
  <div id="bbGrid-clear" class="span8"></div>
</div>
```