- Added Support for Stocks (Total 141 Stocks). Issue: #8

  - Set Index Mode or Stock Mode then select your preferred Index or Stock
  - Values are in 10s in Stock mode and 1000s in Index mode (to compensate for low values of stocks)
  - Symbol of the Stock is present in the names of the .csv files
  - Appropriate Units are reflected in the .csv files
- Added Saving New settings for subsequent runs
  - New Saved settings:
    * Stock/ Index Mode
    * Selected Stock
- Fixed possible issues while reading configuration
- Optimised retrieving data from the API
- All URLs are now in \__init\__ method