HTML5 implementation of a slider (vs. jQuery UI)

[gnestor]

A blocking item for ipywidgets 6.x is to have an implementation of a slider that does not use jquery UI. ipywidgets actually has two types of sliders:

• the classic slider
• the range slider for two values

but the implementation of their views are collapsed into one single class.

We should probably separate these two cases into two different view types and replace the jquery-ui slider with an tag. It is well supported across the browsers supported by jupyter however, the api for styling and making it vertical is a bit browser dependent.

https://css-tricks.com/styling-cross-browser-compatible-range-inputs-css/

The axis widget of the game controller widget should probably also use the range input tag.

Then, we will have the problem of the "range slider" which is a two-values slider.

[gnestor]

Duplicate of #630