Iqplot

- Bring HoverTool specification in line with Bokeh 3 convention.
- Better checking and conversion of categorical variables to strings.

- Addition of spike plots
- Histograms now default to counts, not density
- Bug fixes

Hot fix of bug involved with using `swarm_kwargs` in strip plots.

Added features:

- Swarm plots
- Confidence intervals on histograms
- Stacked arrangement of ECDFs
- Stacked arrangement of histograms (now default)
- Strip-histogram plots
- Staircase ECDFs now hover-able with tooltips

Deprecations

- `jitter` kwarg is now replaced by `spread`.
- `click_policy` kwarg is now replaced by `legend_click_policy`.
- `conf_int_kwargs` is now replaced by `fill_kwargs`.

Quick fix removing deprecation of use of `np.float`.

- Fixed a bug in how outliers were detected and displayed in bar graphs.