Allow HTML string to be passed as context parameter

##### I frequently find the need to render HTML strings that have not yet been inserted into the DOM. I currently do this by...
```javascript
var frag = $('<div/>').html(htmlTemplateString);
frag.render(data, directives);
$('#notifications').prepend(frag);
```
*(this is mostly for lazy loaded templates that don't need to be inserted until after they are rendered)*

##### This commit allows the context parameter on the render method to be an HTML string. The render method then returns a fully rendered DOM node ready to appended/prepended. So, The above code can be made DRYer by...
```javascript
var frag = Transparency.render(htmlTemplateString, data, directives);
$('#notifications').prepend(frag);
```

##### Considerations:
1. The HTML string always gets wrapped in a DIV element. I do not know if this would have adverse affects on rendering; the developer/designer would have to be aware of this as she/he setups their templates. Could the wrapper element be passed in with options param? e.g ````{container: 'span'}````
2. I notice you detach the context element to avoid reflows/paints. This element should not be attached to the DOM at all. I couldn't tell if some code need to be skipped in this case.
3. This was my first experience with CoffeeScript. I did compile and it ran correctly for me.