fix the overly long TOC
Merge pull request #20 from jasonblewis/fix-toc

fix the overly long TOC.
Thanks for Jason's fix.
Extra JS and extra heading attribute.
Add data-transition
Fix a typo
Add workaround for spearker notes blank screen.
Add fragment to source blocks
change org-reveal-history and -roling-links to default nil
feat: add variables for custom title page

REVEAL_TITLE_IMG/REVEAL_TITLE_IMG_WIDTH/REVEAL_WEBPAGE/REVEAL_VENUE
feat: add support "BEGIN_CODE" and "END_CODE" to use highlight.js
feat(ox-reveal): add REVEAL_TITLE_TOP_MARGIN