perform recursive file search when clobbering

ensure all css and css.map files are removed, not just the ones at the root of the /build directory

Author: tagCincy

lib/tasks/clobber.rake

@@ -1,8 +1,8 @@
 namespace :dartsass do
   desc "Remove CSS builds"
   task :clobber do
-    rm_rf Dir["app/assets/builds/[^.]*.css"], verbose: false
-    rm_rf Dir["app/assets/builds/[^.]*.css\.map"], verbose: false
+    rm_rf Dir["app/assets/builds/**/[^.]*.css"], verbose: false
+    rm_rf Dir["app/assets/builds/**/[^.]*.css\.map"], verbose: false
   end
 end