getting rid of VisState
removed functions fireIfVisible, fireIfHidden and fireIfFullyVisible
removed functions fireIfVisibilityChanged and fireIfPercentageChanged
performance; replaced function _findEffectiveStyleProperty with functions computedStyle and styleProperty
removed underscores from functions
added property "code" to state object (former "state"); property "state" now contains a string desription of "code"
test: very update event triggered on call to update()
fixed loader