Added partials client-side template support with { cst: true }

Okay, this commit and pull request is much cleaner.

Here is an example of what this allows you to do:

# some-partial.jade
```jade
each some in someVars
  div= some.name
```

Then `main-view.jade` would get called from something like:

```js
var someVars = [ { name: 'TJ' }, { name: 'Aaron'} ]
res.render('main-view', { someVars: someVars })
```

# main-view.jade

```jade
script#my-template(type='text/template')!= partial('some-partial', { cst: true })
!= partial('some-partial')
```

Output:

```html
<script type="text/template">
  each some in someVars
    div= some.name
</script>
<div>TJ</div>
<div>Aaron</div>
```

:feelsgood: