make category r2c handle strings values
make category r2c handle strings values

- fixes annotations autorange
- does not appear to have any unwanted side-effects.

etpinard/plotly.js,etpinard/plotly.js,aburato/plotly.js,plotly/plotly.js,iongroup/plotly.js,plotly/plotly.js,iongroup/plotly.js,iongroup/plotly.js,plotly/plotly.js,aburato/plotly.js,etpinard/plotly.js,asolagmbh/plotly.js,asolagmbh/plotly.js,plotly/plotly.js,asolagmbh/plotly.js