[core] Stripper doesn't remove trailing " ?"

Query: usage weather ?
DEBUG:plugins.stripper:Message: {'raw': u'usage weather ?', 'deaddressed': u'usage weather ?', 'clean': u'usage weather ', 'stripped': u'usage weather '}
Response: I don't know how to use weather either
Query: usage weather?
DEBUG:plugins.stripper:Message: {'raw': u'usage weather?', 'deaddressed': u'usage weather?', 'clean': u'usage weather', 'stripped': u'usage weather'}
Response: Usage: weather in <city>
Response: Usage: forecast for <city>

The stripper should remove that trailing whitespace too