* Support JavaScript code blocks set apart by triple backticks (``` ... ```)
* Add test for escaped backticks
* Remove TODOs for things we’re never going to support
* Convert escaped backticks to backticks; update tests
* Block inline JavaScript can end with an escaped backtick character
* Updated JavaScript token regexes per @lydell
* In JavaScript blocks, escape backslashes when they immediately precede backticks; additional tests
* Test that we don’t break backslash escaping in JavaScript literals