* Displays a spinner UI while loading PoseNet model

* add empty space at the end of package.json

* rename spinner text

* Converts MobileNet models to graph mode

* fixes posenet_test.ts

* addresses PR comments: 1) Update README 2) Update camera and coco demo 3) refactor the OutputStride to PoseNetOutputStride

* fixes several build errors.

* refactor the GUI update logic in camera demo and COCO demo.

* updates ResNet50 and MobileNet checkpoint URL.