Define beforeEach() in slide_spec

* clean the slide_spec file
Describe .getExampleSettings
Rename 'initialization' to 'init'
Describe #getSettings
Describe .areSettingsValid, add aggressive check

* add "aggressive" parameter to areSettingsValid()
Update setCount() to deny values smaller than 2
ReDescribe setters individually

* describe #setSettings
* describe #getBoxDelays
Simplify #getJs in previewer_spec

* define slideArray and previewerArray