added TTC4900: A Benchmark Data for Turkish Text Categorization dataset
This PR adds the TTC4900 dataset which is a Turkish Text Categorization dataset by me and @basakbuluz. 

Homepage: [https://www.kaggle.com/savasy/ttc4900](https://www.kaggle.com/savasy/ttc4900)
Point of Contact: [Savaş Yıldırım](mailto:savasy@gmail.com) / @savasy
