Add additional function calling models

Hello,

This is in regards of the readme at: https://github.com/abetlen/llama-cpp-python#function-calling. I was reading up on your repo in order to get started/familiar with llam-cpp-python. I want to point out that there are other GGUF quantized LLMs other than functionary that do function calling. And that they are decently good at it from what I hear. Check out https://huggingface.co/TheBloke/Airoboros-M-7B-3.1.2-GGUF#agentfunction-calling for example. May be worth checking out and updating the readme if needed.
There are a few others, but I don't recall them off the top of my head. I may list them here if I do recall or find them.