LlamaIndex v0.4.8

• Added ability to customize text splitter for a given index!
• PSA: all loaders from LlamaHub https://github.com/emptycrown/llama-hub now use llama_index by default instead of gpt_index. If you do not wish to use the llama_index package yet, we've added a use_gpt_index_import option for download_loader. Set it to True, and you can retain gpt_index imports.