added support for includePaths as well as include_paths to middleware.js

lib/middleware.js

@@ -110,7 +110,7 @@ module.exports = function(options){
               fs.writeFile(cssPath, css, 'utf8', next);
             });
           }, {
-            include_paths: [ sassDir ].concat(options.include_paths || []),
+            include_paths: [ sassDir ].concat(options.include_paths || options.includePaths || []),
             output_style: options.output_style || options.outputStyle
           });
         });