let db_config.php include rb.php and initialize database
calculate dividend prices' percentage change into "calculated_percentage_change" table
move functions in show.php into funcitons.php
fixed that cronjob.php didn't save stock_name into database
display title in show.php
add method computeMagicNumbers() for faster calculation
add method getStockNames()
delete_all.php: truncate all tables for testing purpose
add a select box which allow user to select stock
delete old data before calculation
fixed that getAllSurroundingPrices didn't use stock_name as filter