Bug fixes and enhancements

Bugs fixed

• Reconnection used to fail because it tried invoking things from the ReadThread.
• Inferring random ids for ForwardMessagesRequest wasn't working.
• Downloading media from CDNs failed due to having forgotten to remove a single line.
• TcpClient.close() now has a threading.Lock, so NoneType has no close() should not happen.
• New workaround for msg seqno too low/high. Also, both Session.id/seq are not saved anymore.

Enhancements

• Request will be retried up to 5 times by default rather than failing on the first attempt.
• InvalidChecksumError's are now ignored by the library.
• TelegramClient.get_entity() is now public, and uses the @lru_cache() decorator.
• New method to .send_voice_note()'s.
• Methods to send message and media now support a reply_to parameter.
• .send_message() now returns the full message which was just sent.