Selected Dev Building

This pull addresses Brian's feature request in issue #37.

After pulling it, you'll want to delete your build directory. You can run build.sh -h to see details on how to use the new flag.

As a quick example, ./build.sh "examples/SUPERball" will only build the superball example. While ./build.sh "examples" will build everything in the examples folder and below.

The default value when no flag is passed is equivalent to ./build.sh -p "." -- i.e. it's identical to the previous behavior.