Add Reddit dataset

[omarespejel]

Adding a Dataset

• Name: Reddit comments (2015-2018)
• Description: Reddit is an American social news aggregation website, where users can post links, and take part in discussions on these posts. These threaded discussions provide a large corpus, which is converted into a conversational dataset using the tools in this directory.
• Paper: https://arxiv.org/abs/1904.06472
• Data: https://github.com/PolyAI-LDN/conversational-datasets/tree/master/reddit
• Motivation: Dataset for training and evaluating models of conversational response