Allow attributes to be modified and the slider refreshed

Provides a public method to change an attribute of the slider (e.g. min/max, orientation, etc) and another public method to "refresh" the slider (same as creating a new one, but more semantically intuitive).

Includes a unit test showing the orientation change working.

I've found that modifying some attributes post-creation yields some graphical issues (including the orientation change) but those could be overcome as needed. I'm primarily interested in being able to change the min/max and then refresh the slider with those values.