This question is old as **** by know, but in case anyone stumbles upon it I thought I'd chip in with a little tip:
If you are running OSX, there's a nifty little project on Github called Epichrome which allow you to create webapps framed in a native browser-window, much in the same way as Fluid.app is doing – the difference being that for Epichrome-based apps, the underlying engine is Chrome/Blink, and not Safari/Webkit. This in turn enable you to use the same Chrome plugins that you use and love in your Chrome browser, inside your generated site-specific-browser-app. Here's the two first paragraphs from the readme:
Epichrome is made up of two parts: an AppleScript-based Mac application (Epichrome.app) and a companion Chrome extension (Epichrome Helper). Epichrome.app creates Chrome-based site-specific browsers (SSBs) for Mac OSX (Chrome must be installed in order to run them, but they are full Mac apps, each with its own separate Chrome profile).
Each app automatically installs Epichrome Helper, which uses rules to decide which links the app should handle itself, and which should be sent to the default web browser.
I was an avid Fluid.app user before, but have switched to Epichrome since it gives me the same benefits without having to give up the Chrome plugins that I use together with the sites (Trello, for example).
Easiest way to get started is to download one of the release binaries – here's a link to the release notes of 2.1.11 which was released on 22 feb 2016:
Epichrome 2.1.11 release notes
(for the record, I am in no way affiliated with the Epichrome project, I just wanted to present one possible solution to this question).