Version 12.5.1

Released 2020-03-30

Minor changes, doc fixes or bug fixes:

• Add missing docs for PollHandler and PollAnswerHandler (#1853)
• Fix wording in Filters docs (#1855)
• Reorder tests to make them more stable (#1835)
• Make ConversationHandler attributes immutable (#1756)
• Make PrefixHandler attributes command and prefix editable (#1636)
• Fix UTC as default tzinfo for Job (#1696)