Do not forget to collect mercurial servers

Current variant spawns way too many hg instances which are not collected until 
Vim exits.

powerline/lib/vcs/mercurial.py

@@ -63,7 +63,7 @@ class Repository(object):
 		return self.do_status(self.directory, path)
 
 	def do_status(self, directory, path):
-		repo = self._repo(directory)
+		with self._repo(directory) as repo:
 			if path:
 				path = os.path.join(directory, path)
 				statuses = repo.status(include=path, all=True)