Minor modifications.
Made RDD checkpoint not create a new thread. Fixed bug in detecting when spark.cleaner.delay is insufficient.
Use external addresses in standalone WebUI on EC2.
Minor mods
Added metadata cleaner to HttpBroadcast to clean up old broacast files.
Merge pull request #316 from JoshRosen/fix/ec2-web-ui-links

Use external addresses in standalone web UI when running on EC2
Refactored RDD checkpointing to minimize extra fields in RDD class.
Merge branch 'dev' into kafka

Conflicts:
	streaming/src/main/scala/spark/streaming/DStream.scala
Adjust Kafka code to work with new streaming changes.
Added kafka JAR
Don't use bogus port number in notifyADeadHost().
Actually put millis in _lastSeenMs
Track block managers by hostname; handle manager removal.
Add block manager heart beats.

Renames old message called 'HeartBeat' to 'BlockUpdate'.

The BlockManager periodically sends a heart beat message to the master.
If the manager is currently not registered. The master responds to the
heart beat by indicating whether the BlockManager is currently registered
with the master. Additionally, the master now also responds to block
updates by indicating whether the BlockManager in question is registered.
When the BlockManager detects (by heart beat or failed block update)
that it stopped being registered, it reregisters and sends block
updates for all its blocks.
Tests for block manager heartbeats.
Make LocalSparkCluster use distinct IPs
map -> foreach
Don't divide by milliseconds by 1000 more.
Modified checkpoint testsuite to more comprehensively test checkpointing of various RDDs. Fixed checkpoint bug (splits referring to parent RDDs or parent splits) in UnionRDD and CoalescedRDD. Fixed bug in testing ShuffledRDD. Removed unnecessary and useless map-side combining step for narrow dependencies in CoGroupedRDD. Removed unncessary WeakReference stuff from many other RDDs.
Adding locality aware parallelize