Fix number of arguments on `container.addSlider`

[Remco Janssen]

Not sure why this is a problem. Should this be converted to an options object?

Warning: 297:13 warning Method 'addSlider' has too many parameters (5). Maximum allowed is 4 max-params

See: https://bitbucket.org/motiondesign/aequery/src/4fa3668468d17139f7f52924a7b0a4c325842c71/lib/ui/container.js?fileviewer=file-view-default#container.js-297

[Rune Gangsø]

Yeah, option object would be better, and it matches the api of the other addX methods.

Max params is set to 4 because it is difficult to know/nicely code all the params correctly when there are too many. I think after 4 you start struggling with line length and argument order.