initialSlide is numeric and as such it should be treated with parseInt()

[quentinburley]

even though the current handling of initialSlide partially works:
"initialSlide: scope.initialSlide || 0,"
it really ought to be treated with parseInt() to force it into a numeric type, as kenwheeler slick.js expects it to be a numeric type and not a string.
for example in:
https://github.com/kenwheeler/slick/blob/1.5.2/slick/slick.js:399
^^^ (note that here the '+' operator is clearly arithmetic and not a string concatenator).

I suggest

• initialSlide: scope.initialSlide || 0,
• initialSlide: scope.initialSlide != null ? parseInt(scope.initialSlide, 10) : void 0,

as is currently the practice for other params that are to be treated as numeric.

[quentinburley]

proposed fix:
#86