markdown: Changelog

Version Message
1.0.0 - Updated to post 2.1.3 discount version (commit 6eacbc931b)
- Added MarkdownDocument::setReferencePrefix() method.
0.2.0 - Completely new codebase.
- More recent and tightly coupled discount library.
- Much richer interface.
- Interface incompatible with PECL markdown 0.1.0.
0.1.0 - initial release