Support for heredoc style info in ini files, as subclass, with some requisite changes to parents

Hi Ricardo,

Here's a stab at doing this as via subclasses, with minimal changes to the parent classes to improve their subclassability.  Assuming I'm github-ing correctly you should see a series of commits:

1. a pair of commits that fixes a comment in a test file and that adds a label to a `next` statement so that it matches it surroundings better.
1. a commit that adds a test file and some sample data for reading heredoc style ini files
1. a commit that improves the subclass-ability of Config::INI::Reader
1. oops, touch up the reader test
1. Config::INI::Reader::HereDoc
1. a commit that improves the subclass-ability of Config::INI::Writer
1. a test for a heredoc-enabled writer
1. Config::INI::Writer::HereDoc

I suppose I could break Config;:INI::{Reader,Writer}::HereDoc out into their own distributions, but they're awfully minimal....

Feedback?

Thanks!
g.