Fixed Header and Html bugs
- When html is allowed and it was indented, sometimes the code got
converted into code blocks. Fixed that!
- ATX type headers were being converted when a # was found in the
middle of a string. Fixed That too!
- Renamed the escape configuration directive to allow_html
- All data inside a codeblock should be escaped with htmlspecialchars
- Moved filters from the Parser into the Luthor class
- Minor docblock corrections