Andrew fix gg examples

The convention in R is to use 'py' not 'p' when naming the imported plotly module. This updates the sign_in to reflect that.

Note, this isn't yet published. Also, it only effects the *scripts* not the rest of the R code based on the models (json files).

I'd be good to get these merged in and run through all these examples tonight and get them tested/published.
This line could be removed, since `ggplot2` is loaded upon loading `plotly` (line above).