SAMZA-168; add exponential backoff to kafka system admin
SAMZA-166: TestStatefulTask fails.
SAMZA-173; fix NPE when changelog restore includes a message with a null value
SAMZA-169; retry on topic metadata refresh failure in kafka system admin. was ignoring, and losing metadata.
SAMZA-16; fix java 7 test incompatibility
SAMZA-181; add a tutorial to show how to run samza jobs from HDFS.
SAMZA-182; use HADOOP_YARN_HOME instead of YARN_HOME in run-classh.sh.
SAMZA-157; add samza.offset.default configuration for streams and systems.
Seeing issues when running with SAMZA-157, so reverting.

This reverts commit 3a6f2555aa92d47dd85b54f3f1503719c08d31a7.
SAMZA-157; add samza.offset.default configuration for streams and systems.
SAMZA-185: Upgrade Samza to Kafka 0.8.1. Reviewed by Chris Riccomini.
SAMZA-191: Per-SSP poll count metric is overly expensive.
SAMZA-188: Change references in docs to newly hosted ASF hello-samza.
SAMZA-175: Bind AM Jetty server to 0
SMAZA-194: createStreamPartitionString should not use characters that overlap with uris
SAMZA-161: Fix the warnings in check task
SAMZA-174: General-purpose implementation of a retry loop. Reviewed by Chris Riccomini.
SAMZA-193; closing a disconnected KafkaCheckpointManager triggers an NPE
SAMZA-178: Don't catch Throwable, because we want OutOfMemoryError to kill the process. Reviewed by Chris Riccomini.
SAMZA-176: Improve docs for MessageCollector. Reviewed by Jakob Homan.