Release v0.21.5
Merge pull request #660 from plotly/update-readme Refactor Readme and add a contributing doc Former-commit-id: 2bed4b3ea2e6d0c83b78f7af1ad4e2422a31b798
Merge pull request #660 from plotly/update-readme Refactor Readme and add a contributing doc Former-commit-id: 2bed4b3ea2e6d0c83b78f7af1ad4e2422a31b798