Adding file 'batch_rename.scm'

We need a place for the code to go
Changing README.md to explain what the program does and how to use it

Adding 2 sections, What it does and How to use.
Adding --help mode and update in README to same change

For the program to more easily take arguments as well as make using the program much more simple, the way to use the program is changed. You now feed the program the directory containing the files to rename instead of every single file that you would like renamed.