V1.1.0 file downloading

This release contains:

• Added file downloading
• Client refactoring
• Added unit tests to core module

Initial release

Initial version of reactive client to telegram bots API.

What's included:

• Full telegram Bot API support of version 67.0
• Request validation based on JSR-380
• Long-polling support

Future plans:

• File downloading
• Approved spring-native compatibility
• Spring auto configuration module
• Embedded webhook server