Created Ultrasonic example

[mbardoeChoate]

I based this on the java example, but the java Ultrasonic class seems to have some methods that are not in the robotpy, at least not according to the most recent documentation. Therefore I am not using the methods getRangeMM and getRangeInches, but instead show using getRange. If you would like me to do the conversions I can do that.

[virtuald]

Added those methods in https://github.com/robotpy/mostrobotpy/pull/41, go ahead and update the example to include them and we'll merge when I push a new beta release.