SYSCALL 5 uses IOManager
Add write method to IOManager used by SYSCALL 5 to write to the standard
output without using GUIIO.
Error handling in SYSCALL still uses Swing, it needs to be fixed in a
future commit.
Decouple IOManager writes from GUIIO
Add an inner class to GUIIO that extends Writer and can be used  to
represent a file whose writes go to the GUIIO.
Decouple IOManager reads from GUIIO
Add an inner class to GUIIO that extends Reader and can be used to
represent a file whose reads are delegated to GUIIO.
Override correct method of the Writer abstract class
Merge pull request #47 from GraziaCiraulo/master

Decouple SYSCALL from GUIIO