exclude tests top-level package, add some JupyterLab trove classifiers

[bollwyvl]

References

• addresses remove top-level tests module, clean up host deps, test metadata with CLI conda-forge/bqplot-feedstock#86
  • the feedstock will fail downstream once these are removed: this is fine

Code changes

• removes the tests top-level module, which conflicts with other distributions
  • as it's "last-in-wins," this is not a reliable place to put them
  • some downstreams like constructor actively choke on them
• adds some JupyterLab trove classifiers

User-facing changes

• prospective users would be able to see bqplot in the PyPI browse UI when looking for JupyterLab extensions

Backwards-incompatible changes

• n/a

[bollwyvl]

The lint findings seem irrelevant... seems like a single-purpose PR running some formatters would be more helpful than anything else, with the appropriate git history flags to hide the churn.

[martinRenou]

Thanks!

[martinRenou]

meeseeksdev please backport to 0.12.x