Example Scales application written in Scala.js

This is a barebones example of an application written in Scala.js. It has been hijacked as a test harness for developing a Scala-JS version of the Scales library. It will go away fairly soon.

Compile with ~ ;fastOptJS ;test:fastOptJS in sbt, then open index-fastopt.html (and testsuite-fastopt.html for test results).