Add "Troubleshooting dplyr()"

[gilliganondata]

This may make sense as an animated GIF, but could be an addition to http://www.dartistics.com/troubleshooting.html.

Basically, showing how a properly structured set of piped functions can be easily partially executed and inspected along the way by highlight up to just before the pipe at any given point (and then inspecting the data that is passed out of the last highlighted command.