Indicator stroke color and width options

[sgtsquiggs]

Added options to define stroke color (thanks @orsharir) as well as stroke width. Allows the creation of simple hollowed out dots:

pageControl.indicatorDiameter = 5.0f;
pageControl.pageIndicatorTintColor = [UIColor clearColor];
pageControl.pageIndicatorTintStrokeColor = [UIColor whiteColor];
pageControl.pageIndicatorTintStrokeWidth = 0.5f;
pageControl.currentPageIndicatorTintColor = [UIColor whiteColor];