ReDescribe initialization

* rename "construction" to "initialization"
* change "width" to "widths"
* change "customTotalWidth" to "width"
* "widths" can be integer or array from now
ReDescribe setters
ReDescribe #getTotalWidth to work with widths

* "widths" is now either integer or array
ReDescribe #getBoxDelay to work with widths
Describe #getBoxWidth
Describe #getBoxOffset
Update #getCss test suite to use widths
Use "widths" in index.html and main.js
Update JSlider to pass tests

* use "widths"
* define isPositiveIntegerArray(), getBoxWidth(), getBoxOffset()
* update getBoxDelay(), getTotalWidth() and getCss() to use  "widths"
Update UI to use "widths"

* call update() when user unchecks checkbox