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#  NOTE FOR UPGRADING FROM PRE-3.0.0 VERSION     #
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Please note that sinatra-assetpack `img` helper method
no longer sets the image width and height. This default
behavior is not desirable with more recent CSS techniques
regarding high resolutions images for "retina" displays
and "responsive" design CSS using, for example, width:100%.

<img src="retina.jpg" width="1200" height="600">

Is now simply this (unless you explicitly set them) :

<img src="retina.jpg">

See https://github.com/rstacruz/sinatra-assetpack/pull/121