Telemulator3

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- Fix failure on bot command handler (MessageEntity class).

* Method set_tested_bot accept named args `name` and `username` for the tested bot.

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+ Mocked Telegram Bot API elements for unit tests of a bot based on the pyTelegramBotAPI library.

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+ Added `api.set_error` method.

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- Bot `name` and `username` properties moved to api object.

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- Fix missed `json_string` argument in `CallbackQuery` class init.

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* Checks for required pyTelegramBotAPI version on install.