Updated name of method 'trigger' on to 'call' in Callbacks()
Updated implementation of 'show()' & 'hide()' methods. Added method 'toggle()'
Moved constant ATTR_CSS_CORE __def__.PROP_CSS_CORE
Added minor fix for deprecated IE in 'prop()' method
Added minor updates to 'internals.html'
Udpated implementation of 'class manipulation methods' & added appropriate unit tests