Update prompt format

Based on discussion #3 and this GIST https://gist.github.com/the-crypt-keeper/8d781a12ee515903edc89ef69383570f update the chat template to match https://github.com/facebookresearch/llama/blob/main/llama/generation.py#L213

README.md

@@ -48,9 +48,13 @@ GGML files are for CPU + GPU inference using [llama.cpp](https://github.com/gger
 ## Prompt template: Llama-2-Chat
 
 ```
-System: You are a helpful, respectful and honest assistant. Always answer as helpfully as possible, while being safe.  Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense, or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
-User: {prompt}
-Assistant:
+<s>[INST] <<SYS>>
+You are a helpful, respectful and honest assistant. Always answer as helpfully as possible, while being safe.  Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature.
+
+If a question does not make any sense, or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
+<</SYS>>
+
+{prompt} [/INST]
 ```
 
 <!-- compatibility_ggml start -->