GNUmakefile: support for Ruby scripts (as *.rb)
test/welcome: support all languages, not just Python
test/firstarg: inform the user of the argument type
test/welcome: instruct the user to ignore "Error: 1" make messages
test/welcome: rewrap code to < 80-col
New test/firstarg-int: return whatever int is passed
New test/square: return the square of a given number