This patch:
- adds `ElementHandle.boundingBox()` method to get bounding box of element relative
to the page
- adds `ElementHandle.screenshot()` method to capture a screenshot of an element
This patch starts using typescript to lint JSDoc annotations.
Note: this uses typescript's bleeding edge. We should migrate to stable once
it has all the necessary bugfixes.
References #65.
This patch:
- introduces ExecutionContext class that incapsulates javascript
execution context. An examples of execution contexts are workers and
frames
- introduces JSHandle that holds a references to the javascript
object in ExecutionContext
- inherits ElementHandle from JSHandle
Fixes#382.
