Fixed issue 18, thanks pigletto!

git-svn-id: https://django-compress.googlecode.com/svn/trunk@74 98d35234-f74b-0410-9e22-51d878bdf110

compress/filters/csstidy/__init__.py

@@ -15,6 +15,7 @@ class CSSTidyFilter(FilterBase):
     def filter_css(self, css):
         tmp_file = tempfile.NamedTemporaryFile(mode='w+b')
         tmp_file.write(css)
+        tmp_file.flush()
 
         output_file = tempfile.NamedTemporaryFile(mode='w+b')