Unfortunately, `assembly` does not actually invoke `package` at present:

```
jey@kallisti:~/work/spark$ find . -name spark-\*.jar | xargs rm
jey@kallisti:~/work/spark$ find . -name spark-\*.jar
jey@kallisti:~/work/spark$ sbt/sbt assembly 2>&1 | tail -n1
[success] Total time: 27 s, completed Aug 21, 2013 5:56:19 PM
jey@kallisti:~/work/spark$ find . -name spark-\*.jar
./repl/target/spark-repl-assembly-0.8.0-SNAPSHOT.jar
./yarn/target/spark-yarn-assembly-0.8.0-SNAPSHOT.jar
./streaming/target/spark-streaming-assembly-0.8.0-SNAPSHOT.jar
./core/target/spark-core-assembly-0.8.0-SNAPSHOT.jar
```