Add OpenAI's HumanEval dataset
I just fixed the class name, and added `[More Information Needed]` in empty sections in case people want to complete the dataset card :)
This PR adds OpenAI's [HumanEval](https://github.com/openai/human-eval) dataset. The dataset consists of 164 handcrafted programming problems with solutions and unittests to verify solution. This dataset is useful to evaluate code generation models.