Fix an exception thrown when clicking the heading toolbar buttons twice

I believe this one is just a typo
Merge pull request #650 from rebelzach/fix-editor-buttons

Fix an exception thrown when clicking the heading toolbar buttons twice.
Fix broken issues link
Merge pull request #666 from xrd/patch-1

Fix broken issues link
Update README.md

A typo on the fourth word is hard to miss.
Plus some sentence refactoring (because I was already there)
Merge pull request #668 from michaeljoseph/patch-1

Update README.md
Add additional title attributes to links for enhanced screen reader accessibility.
Merge branch 'master' into gh-pages
Update gh-pages branch to deploy new accessibility fixes.
Merge pull request #678 from ndarilek/gh-pages

Deploy accessibility fixes