Remove invoke shower.showPresenterNotes() in enterSlideMode because it already invoked in shower.go()

Fix for #90 + Small JSDoc changes

Fixes for JSDoc & Clean-up

Little clean-up

1.Added methods: shower.isSlideMode() & shower.toggleMode(); 2. All with hash and body.classList are incapsulated into shower.enterSlideMode() and shower.enterListMode() (no more copypaste code in eventListener).

Fix for #77

1. Add callbacks; 2. Move private methods to the begin of methods list; 3. All JS types starts with Uppercase letter