created external variables file (remove dev key later)
verifying file functions work before separating
example working of external function using an external variable
example working of functions and variables from same external file
added checkISBN to sep file successfully
added processISBNFile to functions. made checkISBN internal function only
using only one function file to keep it simple. removed isbnFunctions file
moved most functions to file. kept gnarly ones with external objects in main