Added ReadMe File
Delete README.md
Created another README
Update README.md
Create LICENSE.md
Added License info.
Added AboutBox and MaskedTextbox
Reverted back to Textbox for the input

Decided to validate the input manually
Removed unnecessary types
Created Luhn class and LuhnException class
Finished LuhnException class.

Added an extra label for testing
Finished DigitSum() and Added a new image for About Form
Update README.md
Both overloaded isValid Finished
Added Next Check Digit button and Error handling for strings and empty strings

Even with KeyPress event the user could still bypass the filtering by
pasting the string from the clipboard.
Renamed some files.
Added XML style comments. Started NextCheckDigit(long Number)
Update README.md
Testing new author email.

Just testing.
Testing