Fixed one bug and add two code blocks

[robinbg]

1. Fixed improper data backfill
2. Add codes that downloading price data from yfinance
3. Add codes that generate quarterly data from price and fundamental data

[BruceYanghy]

Data Preprocessing: get a model-ready data inlcudes end-to-end data preprocessing pipline Inputs:

1. price data downloaded from YahooFinance (1996-2022, S&P 500 Components)
2. fundamental raw data，queried from WRDS (1996-2022, S&P 500 Components) Outputs:
3. processed_full.csv，daily data: 693(tics) * 9557 (1996-2022) = 6 million rows data
4. processed_full_quarterly.csv, quarterly data: 693(tics) 26 years 4 quarter=around 80,000 rows data