Twitter v2 streaming API support, changes in messages API

[arkadius]

This change resolves #31. I'm afraid that this change will not be acceptable to merge because it changes almost everything and is not compatible, but if you think different, let me know about it. Changes:

• twitter4j / twitter4j-stream usage was replaced by twitter-api-java-sdk because of a lack of v2 API support
• API of messages was changed. Mainly because Twitter changed it, but also because it was easier for me to keep it 1-to-1 like it in Twitter API - especially, my version doesn't change field names from snake_case to CamelCase
• Some parts of the code were removed at all - like SchemaGeneratorTest and some authentication options. With regards to SchemaGeneratorTest I didn't know how to use it, it looks like util for converter generator, I wrote converter from the scratch without generator. Regarding authentication options - I tested the simplest method with bearer token
• I removed documentation of schema from README.md because IMO it is documented in Twitter API and I see no point in rewritting it to markdown.
• I didn't test this change end-to-end using existing docker-compose.yml and bin/debug.sh - I tested it end-to-end in other project which uses this connector.