fix tests

tests/coverage_server.py

@@ -1,10 +1,10 @@
 #!/usr/bin/env python
 
+if __name__ == '__main__':
     import tornado.ioloop
     import tornado.web
     import urllib
 
-
     class MainHandler(tornado.web.RequestHandler):
         def get(self):
             with open('/tmp/shadowsocks-coverage', 'rb') as f: