Add ignoreAreas into testRun payload

[pashidlos]

New property is added ignoreAreas into request payload and could be processed by server side: Visual-Regression-Tracker/Visual-Regression-Tracker#132
Add ability to pass it as parameter into track method to ignore some parts of image

class IgnoreArea {
  x: number;
  y: number;
  width: number;
  readonly height: number;
}