DataFrame API

• New convenience API including...
  • plot(f, x0, x1): plotting a function from x0 to x1
  • plot(x, y): construct a plot from two arrays
  • plot(df::AbstractDataFrame, ...; group=nothing...): construct a plot using columns of a DataFrame, optionally grouping by a single column to construct multiple traces
• New doc browser: call PlotlyJS.docs() to open an Electron window with a less overwhelming take on the plotly.js chart attribute reference.