Adding missing subsets to the `SemEval-2018 Task 1` dataset
This dataset for the [1st task of SemEval-2018](https://competitions.codalab.org/competitions/17751) competition was missing all subtasks except for subtask 5. I added another two subtasks (subtask 1 and 2), which are each comprised of 12 additional data subsets: for each language in En, Es, Ar, there are 4 datasets, broken down by emotions (anger, fear, joy, sadness).

## Remaining questions

I wasn't able to find any documentation about how one should make PRs to modify datasets. Because of that, I just did my best to integrate the new data into the code, and tested locally that this worked. I'm sorry if I'm not respecting your contributing guidelines – if they are documented somewhere, I'd appreciate if you could send a pointer!

Not sure how `dataset_infos.json` and `dummy` should be updated. My understanding is that they were automatically generated at the time of the original dataset creation?