feat(tooltipProvider): added appendToBody option for $tooltip
feat(tooltip): added appendToBody to $tooltip

Tooltips and popovers can now be appended to the body of the HTML
document instead of directly after the element on which the directive
was invoked, by setting `appendToBody` to true through
$tooltipProvider.options().

The tooltip specs were refactored slightly to bucket all
provider-related specs under a single `describe` for cleanliness.