http://www.valvetime.net/threads/dota-2-workshop-tools-introduce-hammer-2014.245390/
Who knows if we'll ever get it, though.
As you might expect, this 2014 overhaul of Hammer has also introduced some brand new features previously not supported in the older, extremely outdated variants, including Texture Projection for UV Maps, Asset tabs, improved object properties, superior geometry manipulation, a built-in model maker, and an all-new Tile Editor which uses predefined areas to be quickly linked together to form simple gameplay spaces with next to no effort. The editor, while still in development, features a huge variety of other advanced features, as shown by the huge list of recent changes on the Valve Development Wiki.
Who knows if we'll ever get it, though.