Added basic combinators, modified TODO

Adding:
 Section 2 - Selectors:
  Combinators:
   Child combinator,
   Descendant combinator,
   Descendant combinator with defined deepness,
   Descendant combinator with defined deepness range,
   Next-sibling combinator,
   Following-sibling combinator,
   Following-sibling combinator with defined distance,
   Following-sibling combinator with defined distance range,
   Reference combinator
 
 Section 4 - Missing freatures:
  General:
   nth-everything,
   :wrap,
   :event
  Styling API:
   Merge SVG and HTML styling,
   Outline radius,
   Image manipulation,
   Placeholder styling,
   User defined styles,
   Transitions between pages,
   More 3D support

Removing:
 Section 4 - Missing freatures:
  :first,
  :last