Miles/Kilometers selector - pull request

Hello, first of all thanks for sharing FlattestRoute.com with the community. It's very useful, especially in my country Switzerland (there are a lot of steep slopes over here!). The problem is: nobody understands feet and miles here, so I implemented a miles/km selector in this fork a while ago. I am sure a lot of foreign people would use this application if they were able to change units. You can check if my pull request works with the master branch.

Lucien-Media