Move closing of file in Book destructor. This
guarantees us against leaving the file open under
any case and simplifies also Book use.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Let Book be derived directly from std::ifstream
and rewrite the functions accordingly.
Also simplify file reading by use of operator>>()
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>