take 2: Add documentation (#103)

gpt_index/indices/keyword_table/base.py

gpt_index/indices/keyword_table/rake_base.py

gpt_index/indices/keyword_table/simple_base.py

gpt_index/indices/list/__init__.py

gpt_index/indices/list/base.py

gpt_index/indices/query/keyword_table/__init__.py

gpt_index/indices/query/keyword_table/query.py

gpt_index/indices/query/list/__init__.py

gpt_index/indices/query/list/embedding_query.py

gpt_index/indices/query/list/query.py

gpt_index/indices/query/tree/__init__.py

gpt_index/indices/query/tree/embedding_query.py

gpt_index/indices/query/tree/leaf_query.py

gpt_index/indices/query/tree/retrieve_query.py

gpt_index/indices/tree/__init__.py

gpt_index/indices/tree/base.py

gpt_index/langchain_helpers/chain_wrapper.py

gpt_index/prompts/__init__.py

gpt_index/readers/__init__.py

gpt_index/readers/file.py