Release 3.0-beta

• AngleSharp is now the backend parser for Html
• Refactoring to use the Interpreter/Composite design pattern, which ease the code maintenance
• Lots of new unit test cases (~200)
• Rewriting of list (correct handling of nested style, restarting numbers and consecutive)
• Rewriting of table (row span, col span, col tags driving styles)
• Parallel download of images at early stage of the parsing.