WIP for config files
More generic home finding

Reference: https://stat.ethz.ch/pipermail/r-help/2007-March/128217.html
Implement setter and getter for Plotly credentials
Ran roxygenize() from roxygen2
Edit initialization
Update home finding to be generic
Merge branch 'chriddyp-patch-1' into marianne-plotly-credentials
Change setter to overwrite existing credentials with inputs
Shorten lines to less than 80 characters
Merge pull request #37 from ropensci/marianne-plotly-credentials

Plotly credentials tools