CTranslate2 dev env

TODO

• build ctranslate2 cpp code
• build ctranslate2 python bindings
• converting the model from transformers' to ctranslate2 format (fails with a numpy error ModuleNotFoundError: No module named 'numpy._core._multiarray_umath')
• run basic wav2vec2 inference with default lm_head
• run inference without lm_head (return_hidden=true)
• add support for vad_head
• add support for both at once
• make fast
• profit