Add a Gitter chat badge to README.md

### oeyoews/neotw now has a Chat Room on Gitter @oeyoews has just created a chat room. You can visit it here: [https://gitter.im/oeyoews/neotw](https://gitter.im/oeyoews/neotw?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&content=body_link). This pull-request adds this badge to your README.md: [](https://gitter.im/oeyoews/neotw?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=body_badge) If my aim is a little off, please [let me know](https://gitlab.com/gitlab-org/gitter/readme-badger/issues). Happy chatting. PS: [Click here](https://gitter.im/settings/badger/opt-out) if you would prefer not to receive automatic pull-requests from Gitter in future.