Output more TypedCoffeeScript-specific texts

* In REPL mode, TypedCoffeeScript-specific prompt `tcoffee> ` shows that we're using TypedCoffeeScript at present, not using original CoffeeScript.

* Changed the leading comment of compiled script from `CoffeeScript` to `TypedCoffeeScript`. I think this change clarify which file is generated by *Typed*CoffeeScript, and slightly helps us to review the source code later.