diverging.domain([x0, x1][, pivot]) sets the domain from a 2-element extent & pivot

[Fil]

examples:

• d3.scaleDiverging().domain([-10, 145]).domain() // [-10, 0, 145]
• d3.scaleDiverging().domain([89, 145], 100).domain() // [89, 100, 145]
• d3.scaleDiverging().domain([112, 145], 100).domain() // [100, 100, 145]
• d3.scaleDiverging().domain([-112, -145], -100).domain() // [-100, -100, -145]

solves https://github.com/d3/d3-array/issues/132