Minor corrections to v0.20

Updated readme after refactoring.
Updated all method comments.

Reworked renderer

• Reworked rendering, generate a content array rather than creating HTML in order.
• Added a base class so additional rendering classes can be developed.

Attempted to add support for lists, failed at the last hurdle, need to alter how code deals with new lines and then try again.

Initial development release

Initial release, converts delta inserts into HTML, support four attributes,
bold, strike, italic and underline. The HTML tag to be used for each
attribute can be set along with the attributes to use for newlines and paragraphs,
defauls to br and p.