Art/llama3 support

[nivibilla]

Hey,

I was having a look at generalising this to llama 3 70b as well. I found that if we pre convert the safetensors version to a PyTorch pickle version. The model converts fine given the correct config.

And with your tokeniser changes generation should be good too. Pls have a look.

Ive converted and uploaded llama-3-8b-instruct and llama-3-70b-instruct to the native pytorch_model_n_of_n.bin for testing

[nivibilla]

This extends this PR to support both llama 3 8b and 70b.

[Artyom17]

It is great to see that 70B model works as well! Thanks for that! A couple of notes:

1. In your converted llama-3-8b-instruct and llama-3-70b-instruct you misspelled the name of the sub-dir "original" (it is "orignal" in your case), therefore conversion script complains that it can't find the 'tokenizer.model'
2. I afraid, we can't make gpt-fast dependent on a third-party model.

Here is what I think should be done:

1. My original PR gets landed first (really hope it happens soon)
2. It would be nice if HuggingFace adopts your conversion and release those .bin files properly, or
3. We need to add .safetensor-to-.bin conversion script into gpt-fast
4. Finally, you create a proper PR in gpt-fast repo, which adds 70b model support.

What do you think?