range and RangeData in Range.jl

Some comments on `Range.jl`

- The function name `range()` collides with `Base.range()`. Why not renaming it to `rangeslider()` (similar to plotly)?
- You may want to rename the module to `Slider.jl`
- Why do you use `UnitRange` for RangeData? Are you aware that `stop` is modified by the colon operator to have a spacing of `1`?
```
julia> ur = UnitRange(2.3, 3.7)
2.3:3.3
julia> ur.stop
3.3
```