onStart should be called before any update so it should not be wrapped inside a .

perf(initialisation): Remove the timeout call in init.

Closes #220

perf(): Remove $timeout call inside onChange event

When the callback run while changing the slider takes a certain amount of time (~50 ms or more), the
 inside onChange can stall resulting in many changes lost along the way while it catches up.
Removing seems to have no visible side effects. It might be possible that this is due to
scope.() being called right before callOnChange(), so the model is updated anyway (see in
applyModel)

feat(selectionBar): Add a showSelectionBarEnd option

as requested in #213

Set to true to only bind events on slider handles.

Also simplified updateHandles method which was covering some useless cases.

Fixed by adding the tooltip-append-to-body config element to enforce the tooltip to be added to the
body.

Discussed in #209

This feature is similar to the previous ticksValuesTooltip options but for ticks.

Closes #209

Set to true to round the `rzSliderModel` and `rzSliderHigh` to the slider range even when modified from outside the slider. When set to false, if the model values are modified from outside the slider, they are not rounded but they are still rendered properly on the slider.

Closes #208.

Also refactor the tests architecture to have real tests interacting from outside the directive.

The order of watchers definition set the order in which their callback will be called when 2 watched
values are modified simultaneously. If the slider value is changed along with the precision options,
we want the value to be parsed with the new precision.

Closes #207