The line and bar charts under a Coach reply let recharts place the y-axis
ticks over an auto domain, and after thinning the ones that would collide
a blood pressure line could read 75, 90, 105, 135. The chart now computes
a nice domain and hands explicit ticks one step apart (1, 2, 2.5 or 5
times a power of ten); bars keep their zero baseline.
