Update issue tracker link in contributing guide.
STREAMING-50: Support transform workaround in JavaPairDStream

This ports a useful workaround (the `transform` function) to
JavaPairDStream. It is necessary to do things like sorting which
are not supported yet in the core streaming API.
include jobid in Executor commandline args
Merge pull request #461 from JoshRosen/fix/issue-tracker-link

Update issue tracker link in contributing guide
use appid instead of frameworkid; simplify stupid condition
Merge pull request #466 from pwendell/java-stream-transform

STREAMING-50: Support transform workaround in JavaPairDStream
Merge branch 'master' of https://github.com/mesos/spark into WithAB
Merge pull request #467 from squito/executor_job_id

include jobid in Executor commandline args
Avoid a shuffle if combineByKey is passed the same partitioner.
Add assertion about dependencies.
Merge pull request #469 from stephenh/samepartitionercombine

If combineByKey is using the same partitioner, skip the shuffle.
Merge branch 'master' of https://github.com/mesos/spark into WithAB
wip