Scatter Graph fails silently if `data` parameter is not a list.

[radumas]

This took me about an hour of debugging today while playing with my app.

data = go.Scatter(x=df['x'], y=df['y'])
layout = dict(title = 'This won't display')
app.layout = html.Div(dcc.Graph(dict(data=data, layout=layout)))

The above fails silently. The Div will display, as will some of the plotly toolbar, but no Graph will appear. There's no error in the JS console, or the terminal.

Meanwhile this simple change displays the Graph

app.layout = html.Div(dcc.Graph(dict(data=[data], layout=layout)))

[charleyferrari]

@radumas Thanks (belatedly) for writing in. Adding some tags so this can be further discussed.

[chriddyp]

This should be solved as part of #264