Need to unify grid, acnhor and path snapping

[taye]

Use a targets array which contains coordinate objects and functions. Grids would have to be created with an interact.createSnapGrid(gridXY) function;

interact(target).draggable({
  snap: {
    targets: [
      { x: 200, y: 200, range: 50 },

      function (x, y) {
        return { x: x % 20, y: y };
      },

      interact.createSnapGrid({
        x: 100, y: 100,
        offset: { x: 50, y: 50 }
      })
    ]
  }
});

[taye]

Closed in #127