Mapbox token

[Nicolas Kruchten]

Let's please:

1. create a mapbox account under [e-mail] and put the password in 1Password
2. Create a token from that account that's locked to the plot.ly domain name
3. Use that token for JS/Py/R docs
4. make it such that the token is not bubbled through to CodePen

[Joseph Damiba]

@nicolaskruchten These PRs are ready for review. The end state should be that there is no longer any mapbox tokens in CI in these repos.

for JS docs - #1648
for R docs - plotly/plotly.r-docs#8
for python docs - plotly/plotly.py#2035