Clean up
Converters should implement at a minimum 3 methods (matches, convert, output_ext)
Merge pull request #4 from mauriciopasquier/fix-3

Fix #3
Do not assume site.source for everything
Config example, although it doesn't break if it's not present
Erhm.. typo
Merge pull request #5 from mauriciopasquier/configure-output-path

Configure output path