Added

• Add parcats (aka parallel categories) trace type [#2963, #3072]
• Add new gl3d tick and title auto-rotation algorithm that limits text
  overlaps [#3084, #3104, #3131]
• Add support for reversed-range axes on gl3d subplots [#3141]
• Add modebar layout style attributes: orientation, bgcolor, color
  and activecolor [#3068, #3091]
• Add title, titleposition and titlefont attributes to pie traces [#2987]
• Add hoverlabel.split attribute to ohlc and candlestick traces to split
  hover labels into multiple pieces [#2959]
• Add support for line.shape values 'hv', 'vh', 'hvh' and 'vhv'
  in scattergl traces [#3087]
• Add handler for PlotlyConfig.MathJaxConfig: 'local' to override our default
  MathJax behavior which modifies the global MathJax config on load [#2994]
• Add support for graph div as first argument for Plotly.makeTemplate
  and Plotly.validateTemplate [#3111, #3118]
• Implement trace, node and link hoverinfo for sankey traces [#3096, #3150]
• Implement per-sector textfont settings in pie traces [#3130]

Changed

• Use new Plotly logo in "Produced with Plotly" modebar button [#3068]
• Improve histogram autobin algorithm: allow partial bin specification,
  deprecate autobin(x|y) attributes, force stacked/grouped histograms to match size
  and have compatible start value [#3044]
• Count distinct values for category and date axis auto-type, which
  improves the detection of "NaN" string values in numerical data [#3070]
• Improve bar and pie textfont color inheritance [#3130]
• Improve splom first-render, axis range relayout and marker restyle
  performance [#3057, #3161]
• Make splom xaxes and yaxes list always have same length as the trace
  dimensions regardless of their partial visiblities [#3057]
• Improve axis overlaying documentation [#3082]

Fixed

• Fix gl3d subplots on tablets [#3088]
• Fix responsive behavior under flexbox and grid CSS [#3056, #3090, #3122]
• Fix relayout calls turning back autosize on [#3120]
• Fix MathJax rendering (for recent versions of MathJax) [#2994]
• Fix scattergl update on graphs with fractional computed dimensions [#3132]
• Fix scattergl symbols in MS Edge [#2750]
• Fix scattergl selections on overlaying axes [#3067]
• Fix scattergl tozero fills with bad values [#3087, #3168]
• Fix scattergl fill layer ordering [#3087]
• Fix scattergl lines on reversed-range axes [#3078]
• Fix axis auto-type routine for boolean data [#3070]
• Fix splom axis placement when the diagonal is missing [#3057]
• Fix line restyle calls on parcoords traces [#3178]
• Fix parcoods rendering after hovermode relayout calls [#3123]
• Fix WebGL warnings for scatter3d traces with blank text items [#3171, #3177]
• Fix WebGL warnings for scatter3d trace with empty lines [#3174]
• Fix rendering of scatter3d lines for certain scene angles [#3163]
• Fix handling of large pad values in sankey traces [#3143]
• Fix scatterpolargl to scatterpolar toggling [#3098]
• Fix scatterpolargl axis-autorange padding [#3098]
• Fix bar text position for traces with set base [#3156]
• Fix bar support for typed arrays for width and offset attributes [#3169]
• Fix aggregate transforms with bad group values [#3093]
• Fix transforms operating on auto-invisible traces [#3139]
• Fix templating for polar and carpet axes [#3092, #3095]
• Ignore invalid trace indices in restyle and update [#3114]
• Fix grid style relayout calls on graph with large splom traces [#3067]
• Fix logging on some old browsers [#3137]
• Remove erroneous warning WARN: unrecognized full object value when
  relayouting array containers [#3053]