Add support for calling HuggingFace embedding models
using the HuggingFaceHub Inference API. New class mirrors
the existing HuggingFaceHub LLM implementation. Currently
only supports 'sentence-transformers' models.
Closes#86
This fixes Issue #104
The tests for HF Embeddings is skipped because of the segfault issue
mentioned there. Perhaps, a new issue should be created for that?