Try Chrome Dev Tools with built-in workspaces and Emmet Re:View, or NetBeans HTML5 and NetBeans Connector.
I love it. Very clean design. But you don't have breakpoints designed optimally for certain devices.
If you want to check yourself to look at how it looks on various phones, tablets, resolutions - http://re-view.emmet.io/
Re:view is a free chrome plugin. I'm not the author. I use it for development.