Fix jenkins from giving the green light to builds that don't compile.

 Adding `| grep` swallows the non-zero return code from sbt failures. See [here](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/13735/consoleFull) for a Jenkins run that fails to compile, but still gets a green light.

Note the [BUILD FIX] commit isn't actually part of this PR, but github is out of date.

Author: Michael Armbrust <michael@databricks.com>

Closes #317 from marmbrus/fixJenkins and squashes the following commits:

7c77ff9 [Michael Armbrust] Remove output filter that was swallowing non-zero exit codes for test failures.