text: Title: Update Docs / Examples to Use yellowbrick.datasets.load_**
  Body: Building off of:
  https://github.com/DistrictDataLabs/yellowbrick/pull/417
  
  We should update the documentation to use this much easier interface for using our example datasets. 
  
  Docs to Update:
  
  - [x] Readme.md
  
  - [x] Quick Start at http://www.scikit-yb.org/en/latest/quickstart.html
  
  - [x] Model Selection Tutorial at http://www.scikit-yb.org/en/latest/tutorial.html
  
  - [ ] Datasets in the API at http://www.scikit-yb.org/en/latest/api/datasets.html
  