Add 1.4.0 blog post.
Add 1.4.0 to home page.
Show 1.4.0 on builds site.
Add info for 1.5.0 beta to /builds.
Reference run-loop guide from 1.4.0 blog post.
Merge pull request #1291 from rjackson/1-4-0-blog-post

Add 1.4.0 blog post.