    vel.sample(interval)

Sample the underlying SVG element (it currently works only on paths - where it is most useful anyway). Return an array of objects of the form `{ x: Number, y: Number, distance: Number }`. Each of these objects represent a point on the path. This basically creates a discrete representation of the path (which is possible a curve). The sampling `interval` defines the accuracy of the sampling. In other words, we travel from the beginning of the path to the end by `interval` distance (on the path, not between the resulting points) and collect the discrete points on the path. This is very useful in many situations. For example, SVG does not provide a built-in mechanism to find intersections between two paths. Using sampling, we can just generate bunch of points for each of the path and find the closest ones from each set.