Release 1.4

[bbengfort]

• [x] Branch release-1.4 off of develop
• [x] Do version bump (update version listed in yellowbrick/version.py, tests/init.py)
• [x] Run tests
• [x] Create change log/release notes
• [x] Review documentation build
• [x] Merge into master
• [x] Push release to PyPI (python setup.py sdist bdist_wheel, ls dist to check, then twine upload dist/*)
• [x] Create v1.4 tag
• [x] Copy change log to release notes
• [ ] Push documentation to Read the Docs
• [x] Merge release into develop
• [x] Delete release