Fixes #1 for not supporting nested loops

Signed-off-by: Amr Ali <amr.ali.cc@gmail.com>
Fixes #2 where memory cells had an undefined size

Signed-off-by: Amr Ali <amr.ali.cc@gmail.com>
Make Interpreter.interpret() return False to indicate EOP

Signed-off-by: Amr Ali <amr.ali.cc@gmail.com>
Make interpreter indicate EOP when ',' is fed with ''. Closes #3

Signed-off-by: Amr Ali <amr.ali.cc@gmail.com>