Tickmark precision with percentage formatting

[jonmmease]

Originally reported in plotly/plotly.py#1537.

When the axis tickformat is set to 'p' for percentage, the ticks are often displayed with an unexpectedly large amount of precision.

CodePen: https://codepen.io/jonmmease/pen/vMMNXJ?editors=1010

var fig = {
  "data": [
    {
      "type": "scatter",
      "y": [
        0,
        1.0
      ]
    }
  ],
  "layout": {
    "yaxis": {
      "tickformat": "p",
      "automargin": true,
    }
  }
}


Plotly.newPlot('myDiv', fig, {showSendToCloud: true});