styleSheet.rules is non standard, changed to use styleSheet.cssRules isntead. In Firefox, accessing a newly added styleSheet's cssRules too quickly appears to ends up with a DOMException, the try/catch will spin a few more iterations until the styleSheet can be accessed.
Radio and checkbox inputs are not stylable in any browser, deleted the tests that were attempting to test setting unstylable properties on them.
Disabling a TabManager test on Chrome and Firefox due to missing feature, #26 will create a test to replace this one for said browsers. This fixes #157.