None returns from get_int, get_string, ...

[mrijken]

get_int(key) can return a None value. I prefer that get_int (and get_float, get_string, ...) will only return the type which is asked for. As None is not an int, it is better not to return a None from get_int. I need this because I have to wrap all get_int calls with a check for None value.

Are you open for a PR to fix this?