text: Title: Improvements to the Manifold Visualizer
  Body: The following improvements can be made to the manifold visualizer:
  
  *Note to contributors: items in the below checklist don't need to be completed in a single PR; if you see one that catches your eye, feel to pick it off the list!*
  
  - [ ] describe the number of features the embedding represents (e.g. the number of columns in X) and optionally the number of points in the dataset 
  - [ ] create a documentation example for clustering 
  - [x] add `frameon=True` to legend 
  - [ ] create documentation example using the standard scalar 
  - [ ] get the visual tests to work on windows/decrease tolerance 
  - [ ] decrease tolerance of `test_manifold_pandas` (not sure why the tolerance is so high)
  - [x] investigate the `n_neighbors` attribute; see below. 
  
  See #398 #399 