Use svg/icon font instead of png for icons

[ValentinH]

Currently color of icons can't be customized because they are PNG. I think it would be could to be able to change their color to deeper change the customization.

Using icon font or svg is a solution I guess.

[nnajm]

I didn't want to this library depend on external resources (apart from the js & css files) but I think that is unavoidable as more images are needed and embedding images in css limit customization and quality. Will include this in the roadmap (may be next release).