require explicit plotly json encoding by objects
`to_json` was actually used by pandas, and was called by our json encoder before the correct pandas series json encoder was called
add pandas to encoding tests
Merge branch 'master' of github.com:plotly/python-api into fix-pandas-serialization
version 1.4.4 (fix pandas encoding)
sort_keys
mv to single line
ordered keys for testing
Merge pull request #149 from plotly/fix-pandas-serialization

Fix pandas serialization