Deterministic dataset loading
Yes good point ! I think using `sorted(glob.glob())` would actually solve this problem. Can you think of other reasons why dataset loading might not be deterministic? @mariamabarham @yjernite @lhoestq @thomwolf . 

I can do a sweep through the dataset scripts and fix the glob.glob() if you guys are ok with it I'm pretty sure it would solve the problem too.

The only other dataset that is not deterministic right now is `blog_authorship_corpus` (see #215) but this is a problem related to string encodings. I think we should do the same also for `os.list_dir`
When calling:
```python 
import nlp
dataset = nlp.load_dataset("trivia_qa", split="validation[:1%]")
```

the resulting dataset is not deterministic over different google colabs. 
After talking to @thomwolf, I suspect the reason to be the use of `glob.glob` in line:

https://github.com/huggingface/nlp/blob/2e0a8639a79b1abc848cff5c669094d40bba0f63/datasets/trivia_qa/trivia_qa.py#L180

which seems to return an ordering of files that depends on the filesystem:
https://stackoverflow.com/questions/6773584/how-is-pythons-glob-glob-ordered

I think we should go through all the dataset scripts and make sure to have deterministic behavior.

A simple solution for `glob.glob()` would be to just replace it with `sorted(glob.glob())` to have everything sorted by name. 

What do you think @lhoestq?