re-sync with observe-js

[amitport]

Just a reminder to check and merge any bug fixes from observe-js.

[OlsonDev]

You may want to sync my change: googlearchive/observe-js@8ee816a and the updated docs: googlearchive/observe-js@dd278b5

[amitport]

went over observe-js and did not find anything that needs merge for my purposes
(I will merge any feature if someone that uses this lib requests it)