Add support for chrome

[ylecuyer]

Although the dynamic theme API isn't yet available for chrome, we could insert an element in the page like a ribbon on top of the pages with the color

[ylecuyer]

This repo is a proof of concept of envify running inside chrome.

It will have to be merged into this repo when stable.

@Smile4ever would you like to try it ?

[Smile4ever]

@ylecuyer I tested it, looks good. I had some ideas to improve it for Chrome and I have implemented these features locally. If time allows, I will submit a pull request this evening.

[Smile4ever]

See ylecuyer/envify-chrome#3