add Together AI LLM support (#560)

* add Together AI LLM support

* update readme to support together ai

* Patch togetherAI implementation

* add model sorting/option labels by organization for model selection

* linting + add data handling for TogetherAI

* change truthy statement
patch validLLMSelection method

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Co-authored-by: timothycarambat <rambat1010@gmail.com>