Blocks can now be toggled programmatically: $('article:nth-of-type(3)').readmore('toggle')
ARIA semantics describe expanded state and relationship between blocks and their toggles
Blocks are now assigned an ID if they don't already have one
Install development dependencies with NPM
Gulp task to minifiy with UglifyJS
Improvements
Height calculations on window resize are "debounced", resulting in more efficient rendering
Height calculation in general has been improved
The value of the expanded argument passed to the beforeToggle callback now correctly reflects the pre-toggle state
Multiple instances are now fully supported: e.g. $('article').readmore({speed: 200}) and $('fieldset').readmore({speed: 900}) will work on the same page
Fully responsive, plugin now prefers max-heights set in CSS, even inside media queries
Potentially breaking changes
maxHeight option is now collapsedHeight
sectionCSS option is now blockCSS
toggleSlider() method is now just toggle()
Animation is now performed with CSS3 transitions, rather than jQuery.animate()
IE 8 and 9 are no longer supported, because those browsers hate kittens
init() is now called within a window.onload event handler, which can briefly delay collapsing content
setBoxHeight() is now a "private" method called setBoxHeights()
resizeBoxes() is also now private
Readmore.js now uses attribute selectors, rather than classes
The .readmore-js-section and .readmore-js-toggle classes are gone
The expandedClass and collapsedClass options are also gone
Every Readmore.js block needs an ID, if one is not already present, one will be generated
