* added src set as a parsed attribute
* added tests
* changed to /a
* added multiple attribute handling
* added better comment
* made snapshot ignore invalid input as if it is invalid input in the original DOM, it should stay invalid in the recreated DOM
* added extra absolute test case
* code style
* addressed comments
Also move the addHoverClass implementation into the rebuild stage.
So if there is still some corner case we have not handled, it will
only affect the replayer part of rrweb.
