Added readme for browser tests.
Added readme for browser tests.


Former-commit-id: 9fbf459e0aed37f89dbce459c56a15f8d3c5a105
julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine