Fix Extension name
Add package.ini,xml for PEAR installer.
use Twig project extension namespace for markdown extension
Fix Markdown extension namespace

Since Twig_Extensions_* namespace is used for Twig core extension,
And Twig_Filter_* is for twig filter,
we should rename the namespace to Twig_Extension_Markdown
update README and package.xml file
Provide composer.json
update readme for composer
Update document for development
Build package.xml at 2013-01-27
update readme
Merge pull request #3 from c9s/master

PEAR Installer support & Fixing namespace