Create Telegram chat bot.
Use Ruby and related technology stack to create simple Telegram bot to convert Telegram stickers to PNG files.

Requirements:
* Create Telegram bot with configurable ID.
* Implement long polling method to get updates from the API.
* Implement bot command /start. Bot should answer the description.
* When user send some text message, bot should response the warning message with small description.
* When user send some built-in Telegram sticker, bot should response same sticker as a PNG file.
* User should be able to save PNG to the device (phone, computer, etc).
* Use static code analyzer.
* Create Github repository with all code work and valid README file.

Additional score requirements:
* Cover all necessary code with unit tests.

Implementation details:
* Use last stable Ruby version.
* You can use any other gems you want, but make the choice reasonably.
* Write code as clean and as readable as possible.
* Consider using RSpec for testing.
* Consider using RuboCop as a static analyzer.
* Consider using GitFlow workflow.