Add localization example to README

There have been several GitHub issues created in the High Voltage repo around
localization. 

This commit adds instructions for future users interested in localization: https://github.com/thoughtbot/high_voltage/issues/144
good catch. will get this updated. @dgalarza if you have time on Friday would you mind following these steps locally to verify the work as expected? 

I have tested locally- just want to verify this will work as expected for a new user before merging to master.