Shiny application front-end to the Google Directions API

Bethany Yollin has modified the open-source (but poorly maintained) gmapsdistance package. This is a copy of her work. Kyle, Rick, and Mausam are investigating this as an alternative for work they are doing. We may also make additional improvements to gmapsdistance.

Also, this is a great example of a professional shiny app! Open up the R project and the ui.R file in Rstudio and click "Run App" (or type shiny::runApp() in the console).