Update installation instructions

This PR resolves issue #4. Note that I am a complete noob to Maven and Scala, and may be doing this completely wrong.

The installation instructions included in the current README did not work for me for two reasons:

1. The README asks us to run `mvn compile`, but this did not get the dependencies for me.
2. With some research I realized I could get dependencies with `mvn dependency:copy-dependencies`, but this puts the dependency jars in `target/dependency`, not `target/runtime`, which is what the script `examples/iris` requires.

This PR includes an update README that tells users to run `mvn dependency:copy-dependencies` after `mvn compile` (resolving the first of the above issues) and updates the `examples/iris` to point at `target/dependency` (resolving the second).