Attribute name checking only goes 1 level deep

[cpsievert]

This should also warn about yaxis.invalid not being an attribute....

> plot_ly(x = c(1, 2), y = c(1, 2)) %>% add_markers() %>% layout(yaxis = list(invalid = 1), jsksk = list(sadnsa = NA))
Warning message:
'layout' objects don't have these attributes: 'jsksk'
Valid attributes include:
'font', 'title', 'titlefont', 'autosize', 'width', 'height', 'margin', 'paper_bgcolor', 'plot_bgcolor', 'separators', 'hidesources', 'smith', 'showlegend', 'dragmode', 'hovermode', 'xaxis', 'yaxis', 'ternary', 'scene', 'geo', 'mapbox', 'radialaxis', 'angularaxis', 'direction', 'orientation', 'legend', 'annotations', 'shapes', 'images', 'updatemenus', 'sliders', 'calendar', 'barmode', 'bargap', 'mapType'