Change String sounds in FlxSlider to FlxSound's.

[TheGaloXx]

FlxSlider has two variables for sfx, clickSound and hoverSound.
But these are Strings used to give the path of the sound file, not FlxSounds, so the user doesn't have the opportunity to change stuff like the volume, pitch, time, etc.

I think changing these variables to FlxSound would be better to achieve more customization.

FlxG.sound.play(hoverSound); => hoverSound.play();