HR-SR04 and Arduino Nano testing

The idea is to build a very simple HR-SR04 I2C interface and use this to add Altitud capability to my dron improvinf low altitud operations.

First step is the interface the HC-SR04 sensor to arduino nano and then step 2 is suposed to implement I2C communication to APM

Uses the NewPing library that only needs one wire between arduino and the sonar