Adds ChromeOS detection, epiphany browser, and "Chromebook" device model

[eah13]

Not sure if these are useful upstream but I needed to handle epiphany specifically and distinguish ChromeOS from other linux so thought I'd share.

Edit: come to think of it, the device.model addition probably conflates Chromebooks and Chromeboxes, so I could take that out.

[eah13]

Thanks- sorry about that. Forgot to run grunt test and grunt uglify. Was thinking they were wrapped into build

latest commits add iceweasel and midori detection, to round out the common Raspberry Pi browsers.

[barisaydinoglu]

Could you please set version to 2.3.0, thanks :)

[eah13]

Done- thx!