Operator precedence is not being handled

[darkfoxprime]

Operator precedence is not being properly handled. A couple of examples:

>>> to_ast = lambda x:ast.parse(x, mode='eval')
>>> codegen.to_source(to_ast( '(1+2)*3' ))
'1 + 2 * 3'

1+2*3 = 7. (1+2)*3 = 9

>>> codegen.to_source(to_ast( '( "%s " % (sep,) ).join(foo)' ))
"'%s ' % (sep,).join(foo)"

This is evaluated as '%s ' % ((sep,).join(foo)) because . is higher precedence than %

[pmaupin]

The version of this at https://github.com/berkerpeksag/astor handles this properly.