replace the thread with a Akka scheduler
Add spark-tools assembly to spark-class classpath.

This allows the JavaAPICompletenessChecker to be
run with Spark 0.8+.
Don't reset job group when a new job description is set.
Merge pull request #155 from rxin/jobgroup

Don't reset job group when a new job description is set.
Merge pull request #154 from soulmachine/ClusterScheduler

Replace the thread inside ClusterScheduler.start() with an Akka scheduler

Threads are precious resources so that we shouldn't abuse them
Merge pull request #147 from JoshRosen/fix-java-api-completeness-checker

Add spark-tools assembly to spark-class'ss classpath

This commit adds an assembly for `spark-tools` and adds it to `spark-class`'s classpath, allowing the JavaAPICompletenessChecker to be run against Spark 0.8+ with

    ./spark-class org.apache.spark.tools.JavaAPICompletenessChecker

Previously, this tool was run through the `run` script.  I chose to add this to `run-example` because I didn't want to duplicate code in a `run-tool` script.