WIP - adding table of contents (toc) into posts

jquery plugins - `sticky` and `toc` for positioning and
generation respectively

currently still having slight issues with responsiveness
(slight, maybe impossible-to-fix bugs when resized quickly,
easily resolved after a bit of scrolling)

*BUG - can still see the empty TOC (through border lines)*
--> need to fix with better css? when empty the div "collapses"
so the two border lines become one?