:sass filter for a YAML-like CSS styling

A `:sass` filter has been implemented to process the SASS-indented-syntax, a YAML based style-sheet format (somewhat similar to `Stylus`).

The big difference from Stylus is that I have written a Python-based compiler that compiles it directly into CSS within python. You can install https://github.com/boscoh/sassin by ye-olde: 
   
     pip install sassin

with `PyScss` is the only dependency. If this is not automatically installed:
 
    pip install pyscss

If these modules are installed. Then you can write HAML with YAML-like styling:

    %head
       :sass
           #main
             font: Helvetica
             background-color: #AAA
          #footer
             font-size: 0.5em
    #main
       Something
    #footer
       small-print

Gives:

    <head>
    <style type='text/css'>
    /*<![CDATA[*/
    #main {
      font: Helvetica;
      background-color: #AAA;
    }
    #footer {
      font-size: 0.5em;
    }
    /*]]>*/
    </style>
    </head>
    <div id='main'>
       Something
    </div>
    <div id='footer'>
       small-print
    </div>       

A filterSass.hamlpy test has been added for unit-testing.