Scalameter

This is hell. Released version of Scalameter requires Scala 2.10, which
does not work with Java 8. Scala maven plugin has issues with
incremental compilation and Scala 2.11. Whatever. This seems to work,
and the example micro benchmark from the Scalameter documentation can be
run with `mvn scala:run -DmainClass=ChainBenchmark`.
Run benchmark in Graal VM.
Fix mistakes in Truffle usage.

Big thanks to Christian Humer for the patch! :)
Merge branch 'scalameter'