Issue title: Modernizr feature detection
 Issue body: Hi, it is a great work you did there. I have a question, since Modernizr is one of the dependencies, what Modernizr's feature detection does Pushy need? Because as mentioned in Modernizr documentation, use only features detection we need for production.

 Comments: 
 Comment 0: I used Modernizr to detect for CSS 3D Transforms support in the browser, if support isn't detected it uses a jQuery animation fallback.

 Comment 1: I see, anyway will be better if you put feature detection needed in the README.md so other developers know what they need. 

 Comment 2: Great idea. I've updated the README.md with the information. 4393cead4467d7c2a28b6aab68a58fcfbab42016

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