• Add d3.unixDay and d3.unixDays. d3/d3-time#58
• Adopt d3.unixDay in place of d3.utcDay for d3.utcTicks to ensure uniform tick spacing.
• Fix mutation of user-owned thresholds in d3.bin. d3/d3-array#263
• Fix infinite loop when d3.quantile or d3.quickselect is called with invalid arguments. d3/d3-array#262