Cleanup readme to make it easier to read/edit.
Cleanup readme to make it easier to read/edit.

- Use `single backticks` consistently for inline code snippets.
- Add double linefeeds before level 2 headings.
- Add a single linefeed after each heading.
- Minor docs edits.

stefan-langenmaier/reveal.js,tehfedaykin/10CommandmentsofCommunityOrganizing,marc0der/sdkman-talk,jkinkead/reveal.js,siddhartha-gadgil/presentations,fbecart/Presentations,burnpanck/reveal.js,siddhartha-gadgil/presentations,lecovi/reveal.js,agross/git-reveal,marc0der/sdkman-talk,rbtcollins/reveal.js,jlevallois/Kreveal.js,fbecart/Presentations,pascalgrimaud/reveal.js,VisualComputing/Transformations,Jean85/reveal.js,denehyg/reveal.js,rbtcollins/reveal.js,lecovi/reveal.js,hakimel/reveal.js,rbtcollins/reveal.js,rbtcollins/reveal.js,seefood/DIYHolidays,rajgoel/reveal.js,10xEngineer/reveal.js,tehfedaykin/10CommandmentsofCommunityOrganizing,rbtcollins/reveal.js,rbtcollins/reveal.js,lvh/reveal.js,snowyu/reveal.js,christofmarti/reveal.js,VisualComputing/Transformations,benmvp/slides,gapple/myplanet-revealjs,marcusdb/funwithfunctional,stefan-langenmaier/reveal.js,kenkunz/js-crash-course,lvh/reveal.js,benmvp/slides,lecovi/reveal.js,stevedesmond-ca/presentations,kenkunz/js-crash-course,rajgoel/reveal.js,hakimel/reveal.js,jlevallois/Kreveal.js,seefood/DIYHolidays,jayramj/agile-retro,DiUS/reveal.js,stevedesmond-ca/presentations,dbs/reveal.js,maximesinclair/presentations,gapple/myplanet-revealjs,marcusdb/funwithfunctional,denehyg/reveal.js,burnpanck/reveal.js,Jean85/reveal.js,siddhartha-gadgil/presentations,agross/git-reveal,uggla/reveal.js,Gottox/presentations,pascalgrimaud/reveal.js,10xEngineer/reveal.js,soulcharmer/pubquiz_template,maximesinclair/presentations,uggla/reveal.js,DiUS/reveal.js,soulcharmer/pubquiz_template,jkinkead/reveal.js,snowyu/reveal.js,jayramj/agile-retro,christofmarti/reveal.js,dbs/reveal.js