Cleanup

[jbednar]

Miscellaneous cleanup and standardization:

• Update README example to match what is actually in the repo and show correct formatting for keywords as a YAML list
• Move plotnine, pandas, and xarray to a new "User APIs" section as discussed in #93
• Fixed "pyplutchik.yaml" to use ".yml" suffix as on other packages
• Misc cleanup on lots of packages:
  • Deleted stray whitespace
  • Fixed capitalization
  • Added periods consistently to the end of the description field (previously present on 80% but not all)
  • Shortened site URLs to be canonical (removing "/en/latest/", etc.)
  • Made keywords be consistently a YAML list with quotes for multiword keywords
  • Added some keywords where obvious
  • Misc minor fixes and improvements to descriptions

[jklymak]

BTW, this needs a rebase. Feel free to ping for a merge when done.

[jbednar]

@jklymak , done! :-)