Added UIEdgeInsets property for selection controller

Now able to control selection controller horizontal/vertical position offsets through a public property.

_Note_: This does not affect the bounding box of *HMSegmentedControlSelectionStyleBox*
 • When *HMSegmentedControlSelectionIndicatorLocationUp* is selected, bottom edge insets are not used
 • When *HMSegmentedControlSelectionIndicatorLocationDown* is selected, top edge insets are not used