+CalcOpticalFlowPyrLK method

~GoodFeaturesToTrack hardcoded vars replaced with actual parameters

examples/optical-flow.js

@@ -0,0 +1,20 @@
+var cv = require('../lib/opencv');
+
+try {
+  var camera = new cv.VideoCapture(0);
+  var window = new cv.NamedWindow('Video', 0)
+  /*
+  setInterval(function() {
+    camera.read(function(err, im) {
+      if (err) throw err;
+      console.log(im.size())
+      if (im.size()[0] > 0 && im.size()[1] > 0){
+        window.show(im);
+      }
+      window.blockingWaitKey(0, 50);
+    });
+  }, 20);
+  */
+} catch (e){
+  console.log("Couldn't start camera:", e)
+}