First draft of the Asciidoctor.js 1.5.0 release announcement

I'm not really satisfied, maybe we can write more about what's in the release ?
I think I'm too specific on how to use Asciidoctor.js but it's hard to write less. You can't really explain how to use Asciidoctor.js, if you don't explain a little bit of Opal... but do we want to explain how to use Asciidoctor.js in the release announcement ?

I really like the Asciidoctor 1.5.0 release announcement, maybe we can stick with this format ?

 * Highlights
  * Asciidoctor.js is Asciidoctor
  * Node package
  * Bower package


What do you think? 

I recommend switching the attribute from `notitle!` to `showtitle`.